Here I will attempt to assemble a list of essential steampunk novels and where you can pick up a copy.
The Difference Engine (Spectra Special Editions)
by William Gibson - essential steampunk
Extraordinary Engines: The Definitive Steampunk Anthology
- steampunk short stories
Jules Verne's Moon Book - From Earth to the Moon & Round the Moon - Two Complete Books by Jules Verne - all about the moon. Of course there is also 20,000 Leagues Under The Sea (Scholastic Classics)
The The Steampunk Trilogy
- 3 related Victorian stories
For further perusal here is an extensive list http://etheremporium.pbwiki.com/Steampunk%20Essentials