What is steampunk?

Two of Alexis's previous book reviews (City of Bones and Soulless) feature a newly popular sub-genre called "steampunk". What exactly IS steampunk?

There are varying definitions of what makes a book "fit" this classification. Some define steampunk as a type of sci-fi that focuses on the science of the Victorian age (indeed, many of the books--including Soulless-- take place during this time period, but not necessarily all of them). Others suggest it shows people "struggling to push the technology of yesterday into supporting the society of tomorrow." Probably the best definition comes from the Minneapolis Public Library site which states it simply as "Adventures featuring alternate history and low-tech machines that do very high-tech things."

No matter how you define it, the books are worth checking out!