This is a first rate book from O'Reilly. Plenty of depth, to the point that there will be little need to buy any other book on the subject. Here you will learn all about the physical layer, the 802.11 protocol, and plenty of information on the alphabet soup that surrounds it.
The guide is readable and logically laid out. It will make a great reference work but can be read through as a single whole too.
Though old enough to witness how much the 802.11 evolved since 2002, the book stays incredibly useful. The parts we know changed (802.11i, WEP) are causiously explained as well as the why of their weaknesses. A must-read that age as only improved, and a good introduction to its most recent edition!