So here are some of the books I have read this summer that I would highly encourage other musicians to check out:

American Pioneers - Alan Rich (Ives, Cage, Cowell, Varese and more)
The Percussionists Art - Steven Schick (history of solo percussion performance)
Casals and the Art of Interpretation - David Blum
Creative Music Making - William Cahn (a great book on introducing improv. into the classical curriculum)
Touched by Sound - John Wyre
The Inner Voice - Renee Fleming
Silence - John Cage

As you can see a couple of books are about percussion but I also checked out a few other things. I really recommend all of these to any musician, regardless of what you might play.