I have another book recommendation for you
Ben Ratliff, senior jazz critic for the NYTimes, has written a new book (Nov. '08), The Jazz Ear: Conversations Over Music. He asked 15 jazz instrumentalists and singers to pick music, not their own, to listen to with him. Then they sat down to listen and talk about what they were hearing, to very interesting effect. The book is an extension of a series that appeared occasionally in the Arts section of the NYT before the book was published.
This is a terrific read -- snippets of history, reflections on improvisation, glimpses into the mind of some titans, all presented in an articulate, thoughtful, informed way.
Check it out.