Steampunk is usually applied to things that are kinda Victorian in flavor and that usually have fantastic steam powered technology/machines with capabilities well beyond anything the Victorians actually invented. Jules Verne and HG Wells are kinda the great-grandfathers of the genre. The new Sherlock Holmes movie has a mild steampunk flavor to it while the Wild Wild West (both the Wil Smith movie and the original show) are very steampunk (with a western flavor, most steampunk tends to be British in flavor). As for the best book . . . I think the sci fi or fantasy forum had a big discussion on this recently. I'll see if I can find the link.
Looks like there are three that you might like. The links are ugly and may not work. But you can find the discussions by going to the Science Fiction forum http://www.amazon.com/tag/science%20fiction/forum/ and using the Search Discussions box over on the right and look for Steampunk.
And what could be more steampunk than reading classics like Verne or Shelley on an eReader like the Kindle? Life imitating art! I will miss the feel of a good quality leather book cover, though. Fortunately there are plenty of ways to "Steampunk Your Kindle" (accessorize, find other Steampunk eBooks, etc) reviewed over at SteampunkKindle.com