From the one sample I've read (Seventy-seven Clocks) and sampled (Bryant & May On the Loose) the action is much more off-the-wall weird than downright supernatural. This one at least is steampunk, decidedly, with the Victorian ethos cropping up at every turn. Nice if that's your thing. One nuisance thing, though, is that each book has lots of reminiscing about previous cases, so read in order (if you can find them) or skim to avoid spoilers. Dunno if I'd read more, though wiki has an enticing line- "The Victoria Vanishes has similarities with The Moving Toyshop by Edmund Crispin."
This one too has lots of 'helpless folk bullied from above' in it. I don't come across this nearly as much, if at all, in American works, where people are spunky and feisty and bad-mannered in the face of hierarchical idiocy. But it's depressing. Possibly true to life-- the series is back-set in the 70s, about whose corruption Peter has much to say during the course of Moon Over Soho; and the need to placate those in power with an arrest, any arrest, when the victims are upper class and rich, hasn't changed to this day.
It's still lowering to read, so not for those in search of a fun time. Though it does tie in with one theme of The Cure of Souls. There the roots of the action lie back in the early 60s and everyone says 'You can't really realize how different things were back then. People had unquestioned power.' The idea, I guess, being that things suck now but they were infinitely worse forty and fifty years ago. Which has the (unintentional, I trust) effect of making England sound like the Soviet bloc.