True, there's steampunk as a genre of fiction, and there's steampunk as a fashion/art motif.
My favourite work of steampunk fiction is Alan Moore's graphic novel "The League of Extraordinary Gentlemen". Apparently the movie was awful but the comic is quite fun and creepy. The premise is that some real world 18th- and 19th-century fictional heroes (Dr. Jekyll, Captain Nemo, Allan Quatermain, etc.) are actually real, and the kind of technology that appears in their stories is also real. (I will warn for content, because Alan Moore is fond of a) sexual violence and b) ironic racism.)
You could also go one step further back and read actual Victorian speculative fiction, which arguably was the inspiration for steampunk. H.G. Wells' "The Time Machine" is the obvious one.
All that said, I would argue that you don't need to read the stories in order to participate in the art and fashion side of it. If you read the same stories that everyone else has you might just end up with a narrower idea of what steampunk "should" be, and overlook things that you might have come up with to really make your own stuff original.
Ori the Dwarf
Urania, Muse of Astronomy
Random steampunk wardrobe items