For whatever reason, steampunk novels don’t make good movies, or at least haven’t thus far. The best example of this would be the The Golden Compass (2007), which was a box-office flop.
The Sherlock Holmes movie starring Robert Downy Jr. could be considered a moderate success, though the steampunk elements are really an afterthought and it really can’t be considered a steampunk movie.
The League of Extraordinary Gentlemen (2003) is the epitome of a steampunk book being made into a movie and having little commercial or critical success.
What steampunk books would make a good movie
So to look on the positive: what steampunk book would make an awesome steampunk movie?
One has to consider budget, as a story like The Scar (2002, review here) is awesome but might be a bit expensive as its sets would dwarf that of Waterworld (1995).
Of course, since Waterworld computer-generated backgrounds have replaced expensive sets. This is not to say that it should never be made into a movie, but the genre needs a few less expensive hits before we make The Scar for theoretically the sets are much more elaborate than the much maligned Waterworld.
Perdido Street Station by China Miéville
This first book in China Mieville’s Bas-Lag trilogy. A monster versus an adventuring troop story, this would be a fun film introduction to the Bas-Lag novels. It would be an expensive movie to make, but not quite as expensive The Scar.
The Half-Made World by Felix Gilman
This story has a 1970s movie feel to and would make an excellent film. It’s a steampunkafied story of the America West, though set in a completely fictional world, one in which the Western frontier has only partially been created and borders a sea of oblivion.
A Red Sun Also Rises by Mark Hodder
This is a fun surreal steampunk novel whose visuals would translate well to film. Potato with leg aliens talking the Queen’s English. This a simple and fun story that would make an interesting film.
The fact of the matter is that there has never been steampunk story that would be a critical or box-office success. For whatever reason it just hasn’t worked, perhaps it’s just the wrong novels being used.