A very long time in the coming, but worth the wait. This is an exhaustive tome covering an incredible amount of material, from expanding classes, equipment, and dealing with such things as hirelings and so on. The real beauty in this book is that it is just as much a toolbox kit as it is a DMG type of book. It has multiple rule variants, giving alternate options to magic (mana points vs Vancian), wound levels, hit location, multiple critical hit systems, optional skills, optional feat-like abilities, alternate armor rules (ie armor doesn't add to armor class, it soaks damage, etc). You really can design your own game with this book. The optional combat manuevers are a cool tactical option as well.
So besides the standard gamemaster type of subjects you would expect, you also get a lot of stuff to customize the game to your liking. Castles and Crusades is a rules light game but for folks who want to crunch it up a little (or A LOT) can mix up a batch of homebrew goodness with what is in this puppy.
[5 of 5 Stars!]