185 Wireless Secrets is an outstanding book for explaining a multitude of things concerning wireless devices and internet communication with them.  The author talks about unwiring your home or office so that you can be connected without a tangle of wires.  He discusses mobile devices such as PDAs and how to stay connected with them.  He includes the handling of security issues, too, as well as backing up your files.

Jack McCullough has excellent information in the back of the book about wireless manufacturers, internet resources on networking, and mobile wireless applications.

Other topics of discussion are:  the cost of going wireless---it is not as much as you think, how communication works with the internet, the safety of mobile devices, locating access points, hardware and software that you need, dealing with internet providers, expanding the range of your WLAN, instant messaging, and games.

185 Wireless Secrets is a great book for understanding the wireless world.