, each book is different.
As Rust's documentation has grown, we've gained far more than just "The book" and the reference. We now have a collection of various long-form docs, nicknamed "the Rust Bookshelf." Different resources are added at various times, and we're adding new ones as more get written.
Historically, Cargo’s docs were hosted on http://doc.crates.io, which doesn’t follow the release train model, even though Cargo itself does. This led to situations where a feature would land in Cargo nightly, the docs would be updated, and then for up to twelve weeks, users would think that it should work, but it wouldn’t yet. https://doc.rust-lang.org/cargo is the new home of Cargo’s docs, and http://doc.crates.io now redirects there.
Rustdoc, our documentation tool, now has a guide at https://doc.rust-lang.org/rustdoc.
Rust by Example used to live at https://rustbyexample.com, but now is part of the Bookshelf! It can be found at https://doc.rust-lang.org/rust-by-example/. RBE lets you learn Rust through short code examples and exercises, as opposed to the lengthy prose of The Book.