This is a pretty huge book – it doesn't just deliver one complete setting (even with a Plot Point Campaign), it's also a sourcebook for all sorts of Steampunk or Victorian games, be it with magic, aliens, werewolves, clockwork-men, all of it or none of that. I don't know of a single setting (or supplement) that includes so many options and tips on how to run different types of that settings, what novels to read or what movies to watch for more ideas. However, there were a few things missing for my purposes, which is why I can't give it 5/5: The rules and rulings are often a bit loose, so for defined mechanics, I still had to make something up myself (or look into other settings). A few specific setting rules or mechanics would have been nice. The book brings stats for fantastical devices, but doesn't contain prices and stats for everyday stuff like the price of a cab ride or the speed of a steamer. Nonetheless, the Widening Gyre is a great addition to your Steampunk game, even if it might not provide everything you might need.