Yes I saw that... I released mine first but I'm publishing it a chapter at a time and mine is about half done. I haven't read the O'Reilly one because I don't want to inadvertently copy anything or be influenced by it. I think the main difference between my book and this one is that I go through the original BSD source and translate it into idiomatic Rust. I also teach how to work with the borrow checker without resorting to copy/clone or reference counting which I think is unique. And I don't use lifetimes anywhere in the book - they're an advanced topic that really puts off new Rust programmers and aren't needed in most cases.