Author of the book here — yes, I used Mdbook (https://github.com/rust-lang/mdBook https://github.com/rust-lang/mdBook), and the links strangely end with `.html.

Author of the book here — yes, I used Mdbook (https://github.com/rust-lang/mdBook https://github.com/rust-lang/mdBook), and the links strangely end with `.html. as you correctly updated. Initially, I wanted to change it but left it as it was.