There has been a large wave of fandom for this in the past few years. There’s even an anthology of comics (I tried for it; unfortunately I was early in my learning of the Scrivener app and, as a result, I blew it). With all of the popularity I will still try to explain it.
First, here’s the definition on Wikipedia.
The book seen as having launched the genre is The Difference Engine by William Gibson and Bruce Sterling (fathers of Cyberpunk). It has some slight similarities).
I’ve also heard (before the Wikipedia article) it compared to the
works of Jules Verne and H.G. Wells. Verne I can see, though not Wells. Well, for The Time Machine, yes… but not for 1984 or even Animal Farm…
What makes The Time Machine Steampunk is the technology: it’s windup, dials and clockwork devices, not electronics or computerized equipment. It draws some similarities to Cyberpunk in that man and machine are often merged, the difference being that the technology isn’t of the same kind. The former, not the latter.
Although in general fans didn’t like the film remake of The Wild, Wild West much, the film was very much Steampunk-style with all of the windup technology. There wasn’t electricity in that time period.
In essence, Steampunk is science fantasy, not science fiction. I’ll explain the difference in another post.