Essentially, this book makes the assumption that Victorian-era culture, morality, and society would not change much had the technological marvels been possible, and I tend to agree. The setting gives players and GMs a terrific overview of a mis-understood culture that is chock-a-block with gaming possibilities.
As an example, my playing group is using this book to re-create the Battle of Rourke's Drift... but the Prussian government has secretly armed the Zulus with advanced weaponry, in order to win an ally in the region. Is it plausible? Probably not. But is it fun? HECK, YEAH!
Never mind those "more-anarchist-than-thou" cyberpunks or "more-gothic-than-thou" Vampire gamers. Pick up GURPS Steampunk. Pick it up NOW. Trust me.