here's the rendered SUMMARY.md: https://github.com/steveklabnik/rust/blob/new_toc/src/doc/trpl/SUMMARY.md
Basically, the overall structure is this:
- Getting Started - getting an environment up and running
- Learn Rust - project-based learning the basics
- Effective Rust - higher level concepts that lead to writing good rust
- Syntax and Semantics - chunks of exactly what it sounds like
- Nightly Rust - unstable stuff, a staging area for documenting features
- Glossary - self-explanatory