The ARRL Handbook for Radio Communications (2006)
Published by the American Radio Relay League

This book is THE standard wireless reference book 1000 pages of information. If you can buy just one wireless book - this is the one to get!

The ARRL UHF/Microwave Experimenter's Manual
Published by the American Radio Relay League

This book is an excellent microwave theory textbook. It explains microwave theory well without requiring a lot of math.

802.11 Wireless Networks: The Definitive Guide
By Matthew Gast

This is probably the all-around best 802.11 book in terms of providing practical 802.11 knowledge. It primarily covers indoor deployments, but some outdoor information is also included.

Microwave Radio Transmission Design Guide
By Trevor Manning

This is an excellent microwave design book that explains microwave theory at the engineering level, yet it is relatively easy for the non-engineer to use.

IEEE 802.11 Handbook: A Designer's Companion
By Bob O'Haara and Al Petrick

This book provides a good engineering-level view of the 802.11 physical (PHY) and medium access control (MAC) layers.

Broadband Fixed Wireless Networks
By Neil Reid

This book covers some important aspects of deploying license-free wireless WANs. It also includes good information pertaining to licensed wireless networks.

International Microwave Handbook
Published by RSGB and ARRL

The high quality of the theoretical information and the hands-on construction information make this book useful for anyone wanting to gain an in-depth understanding of microwave science and art.

The precursor to this book, the Microwave Handbook, was published by the Radio Society of Great Britain and is currently out of print, but it is a highly recommended three-volume set if found on the used market.

Building Wireless Community Networks
By Rob Flickenger

This books addresses many of the points that need to be considered by anyone who wants to deploy a community network based on 802.11b technology.

Lightning Protection and Grounding Solutions for Communication Sites
Published by PolyPhaser Corp.

This is an excellent book for anyone who wants to have an in-depth understanding of how to protect an outdoor wireless system from lightning. NOTE: This book may now be out of print however you can view online technical briefs and contact PolyPhaser directly for additional information on their currently available publications here.

Wireless LANs (2nd Edition)
by Jim Geier

This is the 2nd edition of the first wireless LAN book available. It provides a good description of 802.11 PHY and MAC-level operation as well as practical techniques that help you to deploy indoor wireless LANs.