This is a great book to understand how to adjust your students. I love the partner yoga section as well. I would highly recommend it to fellow yogis - whether you are a teacher or a student. It's a brilliant reference. It does not cover all alignment principles however, which is something Iyengar students would be paying attention to. Having said that, it is still a great reference to add to your library.
This is book is very well structured and focused. For a newbie in the land of breathing, he certainly gets you into the right frame of mind. It is the sort of book you will refer to over and over again.