Steampunk has gone from being sub-culture to being much more mainstream, and it's inspired many authors to write lots more books. But before you rush to label your work, make sure you understand the genre. Make sure you can answer this question: what's steampunk?
The Sum of Its Parts
To get technical about it, steampunk is a sub-genre of the larger science fiction genre (which isn't at all a bad place to be). All steampunk must have a single element in order to be steampunk: steam-powered engines. If you don't have this, you don't have steampunk.
However, the umbrella could be much wider than you think. The genre does not limit you to the industrialized American or European culture of the 1800s. A steampunk story can be set anywhere in any time -- on a distant moon or in a distant future -- so long as it features the steam-powered machines that marked the early Industrial period.
Because the genre harkens back to the Victorian era, it often features the fashions, art and general styles of the day. Often, technology is enhanced to make the setting much more mechanized than what would be historically accurate. The ideas that marked the era and general inequality is often changed for the sake of steampunk stories, in which women often hold key roles.
H.G. Wells and Jules Verne could both be considered steampunk writers because they envisioned future worlds and grand steam machines. However, the term didn't actually exist until the 1980s (so they were really pioneers). More contemporary steampunk authors include Scott Westerfield and Cassandra Clare.
To learn more about the steampunk genre, research the Victorian Era. It's rich in great ideas and some pretty amazing fashions.