Hacking Movable Type is a new book that promises to become the Movable Type bible. Amazon describes it as:

Gives Web developers and administrators the power to customize and modify MT, from eliminating comment spam and creating customized templates to hacking the MySQL backend and working with third-party modules.

I wish I could see a table of contents, but it does sound like it will be a must read if you are interested in more than just a basic Movable Type installation and need to customize MT to fit your needs.

The authors are:
Jay Allen
Brad Choate
Ben Hammersley
Matt Haughey
David Raynes