This is a great book, that covers the entire world of film scoring in a easily digestible way.
On The Track
This one is next on my list of film scoring books to read. It is very in depth, and has a foreword by John Williams as well as blurbs by many famous composers touting it’s benefits.
The Emerging Film Composer
This is more about the people side of the business of film composing.
Scarecrow Film Score Guides
These are in depth analysis of several very famous scores, including Batman by Danny Elfman, The Good, The Bad and The Ugly by Ennio Morricone, and The Godfather by Nino Rota.