A friend of mine gave me a book entitled A Twist of the Wrist Vol. II. This is absolutely the best thing I have ever read on performance riding and riding in general. If you know nothing, this is the book for you. If you think you know it all, your really should read this one! :)

Everyone swears by that book... I own one, but when I tried reading it... well, it went way over my head. Seemed to be targeted at people riding the track.

I'm a huge fan of Proficient Motorcycling:
http://www.honda599.com/phpBB2/viewtopic.php?t=109

I love to read riding technique books over the Winter. It keeps me connected and I always learn something. Here's my favorites list:

Proficient Motorcycling: The Ultimate Guide to Riding Well by David Hough
More Proficient Motorcycling: Mastering the Ride by David Hough
Smooth Riding the Pridmore Way by Reg Pridmore
Sport Riding Techniques by Nick Ienatsch
Total Control: High-Performance Street Riding Techniques by Lee Parks
The Motorcycle Safety Foundation's Guide To Motorcycling Excellence: Skills, Knowledge, and Strategies For Riding Right by Motorcycle Safety Foundation

I'm also a big fan of the Ride Like a Pro IV DVD by former motorman Jerry Paladino.