diff --git a/src/SUMMARY.md b/src/SUMMARY.md
index 1525076..10a3782 100644
--- a/src/SUMMARY.md
+++ b/src/SUMMARY.md
@@ -47,7 +47,7 @@
 
 - [Generics](ch10-00-generics.md)
     - [Syntax](ch10-01-syntax.md)
-    - [Traits](ch10-02-traits.md)
+    - [Traits](ch10-02-traits.md) - NEED DEFAULT METHOD IMPLEMENTATIONS
     - [Lifetime syntax](ch10-03-lifetime-syntax.md)
 
 - [Testing](ch11-00-testing.md)
@@ -56,58 +56,26 @@
     - [Test Organization](ch11-03-test-organization.md)
 
 - [I/O]()
-    - [`Read` & `Write`]()
-    - [`std::fs`]()
-    - [`std::path`]()
-    - [`std::env`]()
-
 
 ## Thinking in Rust
 
-- [Thinking in Rust]()
-    - [Instead of Inheritance]()
-    - [Trait Objects?]()
+- [Functional Language Features in Rust - Iterators and Closures](ch13-00-functional-features.md)
 
-- [Creating a Library]()
-    - [Cargo]()
-    - [Crates.io]()
-    - [Organizing your Public API](chYY-YY-public-api.md)
-    - [Documentation](chYY-YY-documentation.md)
-    - [Workspaces and Multiple Related Crates](chYY-YY-workspaces.md)
+- [More about Cargo and Crates.io](ch14-00-more-about-cargo.md)
 
-- [Closures]()
+- [Smart Pointers](ch15-00-smart-pointers.md)
 
-- [Zero-cost Abstractions]()
-    - [Iterators as a Case Study]()
+- [Concurrency](ch16-00-concurrency.md)
 
-- [Smart Pointers]()
-    - [`Box<T>`]()
-    - [`Rc<T>`]()
-    - [`Cell`]()
-    - [`RefCell`]()
-    - [Interior Mutability]()
-
-- [Concurrency](ch18-00-concurrency.md)
-    - [Threads]()
-    - [`Send` & `Sync`]()
-    - [`Arc<T>`]()
-    - [`Mutex<T>`]()
-    - [`Channels`]()
+- [Is Rust OOP?](ch17-00-oop.md)
 
 ## Advanced Topics
 
-- [Patterns](chXX-patterns.md)
+- [Patterns](ch18-00-patterns.md) (perhaps an appendix?)
 
-- [More Lifetimes]()
+- [More Lifetimes](ch19-00-more-lifetimes.md) (perhaps merge this into advanced type system features?)
 
-- [Unsafe Rust]() (think about merging into the next chapter on advanced type system features)
-    - [Raw Pointers]()
-    - [`transmute`]()
-
-- [Advanced Type System Features]() (perhaps called "Advanced Traits"?)
-    - [Associated Types]()
-    - [UFCS]()
-    - [Coherence]()
+- [Advanced Type System Features](ch20-00-advanced-types.md) (perhaps called "Advanced Traits"?)
 
 - [Macros]() (think about making little book of rust macros the authority on this topic)
     - [Writing Your Own Macros]()
diff --git a/src/appendix-04-nightly-rust.md b/src/appendix-04-nightly-rust.md
new file mode 100644
index 0000000..f99a3f3
--- /dev/null
+++ b/src/appendix-04-nightly-rust.md
@@ -0,0 +1 @@
+# Nightly Rust
diff --git a/src/ch13-00-functional-features.md b/src/ch13-00-functional-features.md
new file mode 100644
index 0000000..9269638
--- /dev/null
+++ b/src/ch13-00-functional-features.md
@@ -0,0 +1,39 @@
+# Functional Language features in Rust - Iterators and Closures
+
+## Closures
+
+### What is a closure
+
+How are they diff from fns
+
+### `Fn` traits
+
+## Iterators
+
+### Iterator & for loop
+
+.into_iter()
+
+### Iterators are Lazy
+
+Difference between adapter and consumer - another iterator or consuming?
+
+### Implementing the Iterator trait
+
+Talk about using Associated Types here, foreshadow to advanced type systems
+chapter about why this is a different thing than normal
+
+## ??? How does this improve `greprs`
+
+Does this get woven into the above sections?
+
+## Summary: Performance
+
+### Iterators compile down to ASM == for loop
+
+Most complicated chain of iterator functions that compile down to the same ASM as a for loop
+
+### Representation: Closures are a Struct
+
+Closures don't have any further perf penalty over regular fn calls
+
diff --git a/src/ch15-00-smart-pointers.md b/src/ch15-00-smart-pointers.md
new file mode 100644
index 0000000..5273b49
--- /dev/null
+++ b/src/ch15-00-smart-pointers.md
@@ -0,0 +1,112 @@
+# Smart Pointers
+
+By smart pointers we mean a reference with more characteristics.
+
+Example of something that doesn't work
+
+Surprise! Vec and String are technically smart pointers too!
+
+This chapter is not a comprehensive list, but will give some examples of the
+ones in the standard library.
+
+
+## `Box<T>`
+
+Don't use very often in your own code
+Heap allocated
+Express Ownership of a heap allocated thing
+
+The three situations to use Box
+
+1. Trait objects
+2. Recursive data structures
+3. Extend the lifetime of something
+
+How this interacts with the Drop trait
+
+## `Rc<T>`
+
+Reference counted. Rc is for *multiple ownership* - this thing should get
+deallocated when all of the owners go out of scope.
+
+Show the data structure:
+
+```rust
+struct Rc<T> {
+    data: Box<T>,
+    strong_reference_count: usize,
+    weak_reference_count: usize,
+}
+```
+
+Talk through this.
+
+This only works if the data is immutable.
+
+What happens when you clone an Rc: data isn't cloned, increase the strong count.
+When an Rc clone goes out of scope, the count goes down.
+
+### Rc Cycles
+
+This is how you leak memory in rust, which btw is totally safe.
+
+Is this garbage collecting? Well it's not tracing GC...  if you use Rc and had
+a cycle detector, it would be functionally equivalent to a tracing GC. Different
+runtime characteristics tho.
+
+
+#### Solution: turn an Rc into a `Weak<T>`
+
+Same as Rc, but doesn't count towards the strong ref count. When you do this, the
+strong ref count goes down and the weak count goes up.
+
+Data gets cleaned up when the strong count is 0, no matter what the weak count is.
+
+Why is the weak count needed then????
+
+
+## `RefCell<T>`
+
+Single owner of mutable data
+
+The ownership rules checked at runtime instead of compile time.
+
+Only single threaded. See next chapter.
+
+### `borrow` and `borrow_mut` methods
+
+Checks all the rules and panics at runtime if the code violates them.
+
+1. The borrow checker is conservative and people can know more things. (no you
+don't, but if you really want to go back to debugging segfaults, feel free)
+
+2. For when you're only allowed to have an immutable thing (which could be `Rc`)
+but you need to be able to mutate the underlying data.
+
+## `Cell<T>`
+
+Same thing as RefCell but for types that are Copy. No borrow checking rules here
+anyway. So just reason #2 above.
+
+## Is this really safe? Yes srsly
+
+RefCell is still doing the checks, just at runtime
+Cell is safe bc Copy types don't need the ownership rules anyway
+
+### The Interior Mutability Pattern
+
+The Interior Mutability Pattern is super unsafe internally but safe to use
+from the outside and is totally safe, totally, trust us, seriously, it's safe.
+
+Allude to `UnsafeCell<T>` maybe. Affects optimizations since &mut T is unique.
+UnsafeCell turns off those optimizations so that everything doesn't break.
+
+This is how you can opt-out of the default of Rust's ownership rules and opt
+in to different guarantees.
+
+## Summary
+
+If you want to implement your own smart pointer, go read the Nomicon.
+
+Now let's talk about concurrency, and some smart pointers that can be used
+with multiple threads.
diff --git a/src/ch18-00-concurrency.md b/src/ch16-00-concurrency.md
similarity index 64%
rename from src/ch18-00-concurrency.md
rename to src/ch16-00-concurrency.md
index 9c32ee7..9bed80f 100644
--- a/src/ch18-00-concurrency.md
+++ b/src/ch16-00-concurrency.md
@@ -1,17 +1,101 @@
-# Concurrency
-
-This is a really rough sketch of some ideas that this chapter might cover.
-
-From a comment of steveklabnik's on [the orange website]. "that paper" refers to [Boehm 2004].
-
-[the orange website]: https://news.ycombinator.com/item?id=13078384
-[Boehm 2004]: http://www.hpl.hp.com/techreports/2004/HPL-2004-209.pdf
+# Fearless Concurrency
 
 So, with Rust, it's more subtle than that. That is, while threading proper
 isn't part of the language itself, Rust's type system is structured in such a
 way as to make it possible to build those kinds of libraries. In other words,
 Rust's focus on aliasability ends up solving these problems.
 
+This is a library abstraction.
+
+Shared mutable state is a problem. Both useful. Functional langs get rid of
+mutability.
+
+Ownership rules (that tame the "shared" aspect) enable fearless concurrency: the
+compiler is making sure you don't shoot yourself in your foot.
+
+## What are threads
+
+
+
+## Rust's concurrency tradeoffs
+
+Lots of different languages tackle this problem in different ways. We are not
+going to talk about that: exercise for the reader is investigate other langs
+and compare and contrast with Rust's approach.
+
+This is how Rust does it, what rust means by threads
+
+OS threads are exposed in the standard library bc a systems programming language
+should integrate with your system.
+
+If you have a different threaded mechanism, you need a runtime, rust is trying
+to not have a heavy runtime.
+
+These are the reasons Rust's concurrency model is this way as opposed to other
+lang's ways, which are optimizing for different things.
+
+
+## Let's get a thread: `thread::spawn`
+
+Code examples - just print stuff, no data sharing
+
+## Communicating between threads
+
+### `Channels`
+
+Look up examples of cases where channels are useful
+
+Can match modeling of certain problems
+
+#### `Send`
+
+Send is a trait that means i'm allowed to transfer ownership to another thread
+down a channel
+
+What things can be send and what can't?
+
+## Sharing data between threads
+
+Try to share data and get an error about which trait it doesn't implement
+
+### `Sync`
+
+It's ok to access a thing from multiple threads at once
+
+Immutable things can be sync easily.
+
+### `Arc<T>`
+
+Atomic Reference Counting. Inner data still has to be immutable.
+
+Steve knows the motivating code that goes here.
+
+### `Mutex<T>`
+
+For mutabe data.
+
+`lock` method, you get a Mutex guard. Change, then unlock, which usually happens
+automatically when the Mutex guard goes out of scope. If you do this wrong, your
+code will hang.
+
+Deadlocks are safe, you have to manage that yourself. Deadlock bugs usually
+happen bc you forget to unlock, but drop unlocks automatically.
+
+
+## Maybe make `greprs` concurrent?
+
+Might be boilerplatey without scoped threads, maybe just allude.
+
+
+
+This is a really rough sketch of some ideas that this chapter might cover.
+
+From a comment of steveklabnik's on [the definitely not orange website]. "that paper" refers to [Boehm 2004].
+
+[the orange website]: https://news.ycombinator.com/item?id=13078384
+[Boehm 2004]: http://www.hpl.hp.com/techreports/2004/HPL-2004-209.pdf
+
+
 So for example, in that paper, 4.1 is about the problem of concurrent
 modifiability. And indeed, it says
 
diff --git a/src/ch17-00-oop.md b/src/ch17-00-oop.md
new file mode 100644
index 0000000..7d0018e
--- /dev/null
+++ b/src/ch17-00-oop.md
@@ -0,0 +1,73 @@
+# Is Rust OOP?
+
+Aphorism: DRY
+
+So how do you share code?
+
+I'm used to doing things to solve problems, what do i do instead?
+Why do i need to do different things in Rust? Let's look at an example
+with the Command pattern.
+
+## Command pattern
+
+Look up official def
+
+Want caller to be able to customize what gets done
+
+Method takes command object, calls a run fn
+
+How do we say "we want a thing that has a run function"? Answer: Traits!
+
+where T: Run
+
+This is the definition of the Fn trait! So we wouldn't implement this, we'd just
+pass closures in
+
+## Supertraits
+
+Trait constraints that use other traits
+
+Copy requires Clone because Copy is a subset of Clone's behavior, since if you
+have one, you can trivially implement the other.
+
+Traits that need behavior of another trait in a default method or something.
+
+## Trait objects
+
+Runtime decisions about deciding what shared code we use
+
+Give example code
+
+With traits, libraries are extendable. This is why trait objects are different
+than having an enum and a match statement that has to be exhaustive at compile
+time and we have to know all the things at compile time and no one can add
+new things to the set of possible things
+
+T: trait is a compile time decision, monomorphization == static dispatch
+
+when you implement this trait, you get this other shared behavior
+
+dynamic dispatch (C++)
+
+### Implementation details
+
+- Like how other languages implement oo.
+
+### How to use it
+
+- Statically checked duck typing
+
+## Builder pattern
+
+When you don't know how many arguments you're going to have
+
+## Delegation
+
+Deref - be mad
+
+Deref is a way to delegate everything, if you don't want that, then write
+boilerplate. Sending messages to your components.
+
+## How do you share data?
+
+Answer: get and set methods, this is awkward and might get better someday.
diff --git a/src/chXX-patterns.md b/src/ch18-00-patterns.md
similarity index 100%
rename from src/chXX-patterns.md
rename to src/ch18-00-patterns.md
diff --git a/src/ch19-00-more-lifetimes.md b/src/ch19-00-more-lifetimes.md
new file mode 100644
index 0000000..535e161
--- /dev/null
+++ b/src/ch19-00-more-lifetimes.md
@@ -0,0 +1,11 @@
+# More Lifetimes
+
+## Lifetimes that depend on other lifetimes
+
+'a: 'b stuff: subtyping
+
+## Higher ranked trait bounds
+
+for<'a>
+
+Needed for closures
diff --git a/src/ch20-00-advanced-types.md b/src/ch20-00-advanced-types.md
new file mode 100644
index 0000000..51f4899
--- /dev/null
+++ b/src/ch20-00-advanced-types.md
@@ -0,0 +1,56 @@
+# Advanced Type System Features
+
+## Unsafe Rust
+
+Things you may do in an unsafe block that you may not in safe rust
+
+- deref a raw pointer
+- call an unsafe fn
+- access or modify a static variable
+- impl an unsafe trait
+
+Go see other stuff
+
+Here's the syntax tho
+
+You know unsafe blocks are the cause of any crashes
+
+wrap all the unsafe, make it as small as possible, present a safe public API
+
+### Raw Pointers
+
+### Unsafe Functions
+
+#### `transmute`
+
+never ever. don't. stop.
+
+#### `extern fn`
+
+You have to write unsafe code to FFI
+
+### `static`
+
+### Unsafe Traits
+
+## Associated Types
+
+More common than the other things, less common than the rest of the book
+
+why this is a thing instead of a generic
+
+## The Thing Formerly Known as UFCS
+
+Only needed when implementing super generic code
+
+Lots of things are syntax sugar for this
+
+Two traits that impl the same method - how to disambiguate
+
+## Coherence
+
+Show examples of when you control traits and types or not
+
+Ex: Cannot impl Debug on someone else's type
+
+Solution: newtype