TDE is considered something of a steampunk classic, and it is certainly a book that contributed a great deal to the popular tie-in of steampunk and Victorian England. Contrary to the often garish, predominantly visual, subculture that has arisen in recent years, the version of the genre presented in this novel is somewhat subdued. It is mostly a detective tale, though with its fair share of espionage, subterfuge, and action. What makes it steampunk is the prominence of steam technology used for transportation and racing on the one hand, and for use in punchcard-driven computing and visualisation (kinotropy) on the other.
Despite its original setting and canonical status, the book left me somewhat cold. The plot was exciting enough, but the technological peculiarities featured more as objects and backdrops than as elements that deeply influenced the world in which the story unfolds. In this sense, TDE falls a bit short in the department of raising questions about technology and society, which in my opinion is one of the main functions of science fiction. There are hints here and there towards the way in which steam computers and dreadnought battleships might have influenced history, but not as many as you'd expect or perhaps would have liked to see.