From the back cover:
The definitive d20 system resource for steampunk fantasy settings and adventures.
A comprehensive discussion of what steampunk is, what it looks and feels like, and how to introduce it into your fantasy game.
Detailed guidelines on incorporating the existing core classes into a steampunk game, along with thee new classes and more than a dozen prestige classes.
A handful of new skills, including Drive, Munitions, and Use Steamcraft Device, as well as new uses for existing skills.
Detailed information on new equipment and technology, from steamcraft devices to black powder weapons.
Comprehensive vehicle rules and descriptions of several common steamcraft vehicles, including locomotives, ironclads, and zeppelins.