I'm currently reading Keith Code's Twist of the Wrist II. I heard the first one isn't quite as good. There's a good deal of info on shifting weight, and bad riding techniques you should overcome. Good stuff, especially if you plan on doing track days. Got it on eBay for $9 shipped, you can get it at a bookstore for $19 or so.
If you want to read something more oriented to street riding than track (i.e. looking out for real-world 'gotchas') you could try any of the David Hough books (Proficient Motorcycling, More Proficient Motorcycling and Street Strategies). Personally I found the first one to be the most engaging (Proficient Motorcycling).