20,000 leagues under the sea is considered to be a "steampunk" book. I can't think of any others off the top of my head. Glancing at wikipedia, it claims books like "The Time Machine" also helped define the genre.
I would argue that steampunk is usually very dystopian. but when I think about it, most of the common ones you might find in pop culture, they aren't.
When I think "steam punk" I think of very dark grizzled settings, locked in some sort of conflict where guys march around in steam-powered suits like what inspired Big Daddies in Bioshock, shooting WW2 style mustard gas cans and flame throwers. All the while the people struggling to survive in this doomed setting scramble to hide in the broken down shelters as the inspired mechanics make trinkets out of abandoned tanks.
An alternate setting is something perhaps a little brighter with magic present, where goblins make mechinized suits in smelting plants from troll mined ore. And mad magicians replace broken limbs with magicially enhanced mechanical limbs. This is a bit closer to the more 'pop culture" version of steampunk.
I think people when they hear "steampunk" think of things like the Steamboy, Lock's Quest, Gatheryn, or certain parts of Warcraft. Which I would agree, do represent something akin to what I'd expect from "Victorian Steam Age" influence, but I wouldn't call "steampunk" exactly. (well, I would call steamboy steampunk based on the themes of the story, but not the other examples)
If you don't think BioShock, Thief: The Metal Age, Metropolis, or the Last Exile represent dystopian settings, I'm... I'd likely respect your opinion, but I think they do. Back in the day, I always called settings like this "victorian steam age" settings, but in the last few years I have adopted "steampunk" to be the name of the genre and with it include any technology based, pre-modern, settings with dark and gritty overtones.
As suggested by SmallTrippin's post about authors, Cyberpunk certainly has a lot more literature to draw its style when compared to Steampunk. And I think that Cyberpunk has many more examples of extremely dark and dystopian settings. However, I feel this is an injustice to Steampunk as a genre that we should not hold against it. I would possibly list the movie "Wizards" as "Steampunk" if I was pushed, even though it has no steam engines in it to what I'm aware. It certainly isn't "Cyber" and I feel "Dieselpunk" or "Combustionpunk" seperating from Steampunk is splitting hairs. I might even go as far as to include "Vampire Hunter D" as at least partial steampunk, though its got enough "Cyberpunk" stuff like biomechanical horses in it that it could go either way. I imagine its labs to be filled with things like what a mad scientist of the 1800s-1900s would have, which is why I think that. Depends on how you invision it I suppose.
Like I was saying about reverse steampunk. It would have to be not-steam (which means removal of anything that would look in place in steamage industrial settings) and not-punk (which means removal of all things "punk" by any definition relating to genre).
