Recommended books:

CWNA Certified Wireless Network Administrator by Sybex
If you are new to Wi-Fi, this is number 1 book to buy. Don’t worry if you don’t understand some concepts during first reading. This is normal. Many engineers go back to this book and read it again as it is great resources.

CWSP Certified Wireless Security Professional by Sybex
All security related features explained.

CWAP Certified Wireless Analysis by Sybex
Frame by frame analysis.

CWDP Certified Wireless Design Professional by Sybex

Next Generation Wireless LANs: 802.11n and 802.11ac 2nd Edition by Cambridge University Press

more to come