I'm reading Burton Richardson's new book, and I absolutely love it. Burton is a great writer (in my opinion), and that makes it hard to put the book down (just ask my wife).
It has a lot of information about chokes and how they work (and why we should use them). It also covers taking the back and keeping the back. I've never seen so much information on that subject before. In fact, it has a lot of BJJ information that is new to me.
I'm going to be learning from this book for a long time. I highly recommend it.