Robot Reading: There are a lot of books out there on this subject now, and more coming out all the time.

General:

• Mobile Robots, 2nd Edition by Joseph Jones/Anita Flynn/Bruce Sieger - Considered by many to be the bible of robot building. Certainly it is a good text and useful reference, and it does cover the subject well, but if you're a rank beginner with little electronics experience, you might try Robot Building for Beginners.
• Robot Building for Beginners by David Cook - If you have no experience with electonics, then Cook's work is a good starting place. He covers very basic subjects in depth and walks you slowly through what many books breeze over. However if you know what a voltage divider is already then you'll probably find this text TOO basic.
• The Robot Builder's Bonanza by Gordon McComb. A bit older of a book and some of its solutions use technology that is a bit out of date. But it's a great book. I'd recommend it to beginners and more experienced alike. I got inspiration to start using metal and other materials from this book and for that reason alone it is a good one to have on the shelf. And you can get this one cheaper than the others generally.
• Robots, Androids, and Animatronics by John Iovine. Really good treatment on general subjects combined with step by step instructions for several good projects. I based my Walker robot on a design in this book. He covers other topics like voice recognition devices very well as well. I recommend this book highly if you like a book that not only gives ideas, but very specific drawings and "connect part A to the back of part B" type instructions.
• Build Your Own Robot by Karl Lunt - The first book I got on this topic and it inspired me to get going and building. I owe Mr Lunt a big thanks. I took this book with me to Seattle to the Seattle Robotics Society's Robothon '02 to have him sign it. Then I left it in my room. Oh well. This book is full of great stuff, but it may be hard to find. This book is a compilation of his articles from Nuts and Volts for years, and his articles tackled a number of subjects each month. So the Table of Contents and the Index may not find you what you want. You may have to thumb through it. I made my own index for this box. I don't recommend this as a first buy, but do get it.
• Applied Robotics by Edwin Wise. About everything you see in this book is covered elsewhere. The illustrations are not as impressive as the others. Of course, Wise hits on devices and topics that the other guys don't. I recommend this after you get the other ones though to round out an already basic library.

Specialized:

Build Your Own Underwater Robot by Harry Bohm - Fantastic book if you want to build a quick underwater robot. He keeps it very simple and you can use his instructions to crank out a submarine robot FAST (I could pull it off in 4 hours I think). The robot will be a bit simple. Max depth will be about 10' and the control a bit rough, but what the hey. It got me going. Good starting place.

Building Robot Drivetrains by Dennis Clark and Michael Owings - The general topic robotics book has been done pretty well. So these guys tackled a specialized topic. Drivetrains, the guts that makes the thing move. They cover this topic well, thoroughly discussing H bridges and control circuits which you'll get in the basic books, but also tackling the mechanical stuff. Linkages, how to mount the motor so you get efficient transfer of force, how to figure out required torque and to DESIGN your robot's drive rather than take guesses and hope it works. It is filled not just with equations though. They summarize into quick rules of thumb wherever possible. Great book. I highly recommend this if you are going to build from scratch.

Unofficial Guide to Lego Mindstorms Robots by Johnathan Knudsen - First off let me say that I'm not wild about Lego Mindstorms. You can do cool stuff with it, but for me where it's at in this hobby is building from scratch. Having said that, this is a good book. If you want to get into Lego's pick this up. It covers the basic stuff like the books that come with the set, but it also gives you a good treatment on expanding into using the NQC (Not Quite C) compiler that you load as new firmware and how to program in it.