Speculative Fiction (SciFi/Fantasy) has often taken the possible and impossible to explore new worlds or our world in alternate times or histories. Within that larger genre are many subgenres. Amy Goldschlager (Avon/EOS) provided an explanation of several of the different subgenres in 1997. You can read her listing here .
In the years that have passed, some genres have brightened and others dimmed. Particularly paranormal mysteries have taken off with books like Charlaine Harris’s Sookie Stackhouse series . Steampunk was a genre long before it was a fashion statement – H.G Wells and Jules Verne anyone? Of late, I’ve been stretching out of my epic fantasy trend (who doesn’t enjoy a good 1083 page Tad Williams third book in a trilogy now and then?) to reach into the Steampunk subgenre. A great start is the Extraordinary Engines  anthology. The short stories show the variety of Steampunk, from great steam-propelled boxers to airships.