Literature Highly Recommended
I can't remember exacty what made me pick up the first book in Waterstones, but I do know that a week later I had a copy of every single one published and was most of the way through reading them. Peter is a bit of an asshole protagonist for the first couple of books, but his narration of the events (both insightful and hilarious) meant I couldn't help liking him and enjoying being in his head.
The world building is beautifully done, merging common knowledge of the real world and made-up fantasy pretty seamlessly, and it comes gently and naturally throughout the series rather than in exposition dumps. The characters are all excellent fun to read about, whether they're villains or heroes or neither. However, there are quite a lot of them and when considered alongside the plot of the individual books and the plot of the series as a whole, it's very easy to lose track of just what's going on in your first reading.
Despite my confusion at what was happening in the books I still greatly enjoyed them and would recommend them to anyone who enjoys The X Files, Johnathan Strange and Mr Norrell or Discworld. They have a lovely blend of crime and fantasy, humour and horror - just make sure you have enough time to read them through properly!
Literature Ghostbusting, by the Book
This seems like a book made for anyone who enjoyed Men in Black. It's got the same deadpan, banal approach to the extraordinary. Also, it too happens to be about a young black cop who gets inducted into a secret world by an old white official who's job it is to protect the mundane from the paranormal.
Specifically, London is overflowing with all manner of cryptids, ghosts, wizards, nymphs and all kinds of nasty surprises, and our protagonist, Peter, is thrust into it headfirst by an old fashioned, Inspector Morse / David Niven type detective. Peter is a fun protagonist. He's geeky, shy, sexually frustrated bloke who consequently is doomed to a life in admin. As such. he's full of wry opinions on police work, culture, history and race.
Rivers of London is a light mystery, so don't expect any major philosophical detours. Its committed chiefly to solving a mystery and having a bit of a laugh on the way. That doesn't stop it from having some genuinely unpleasant twists though, and the comedy often serves to disguise the ambushes. The only thing readers should be aware of is that there a lot of English references and slang, which is fine if you are from the UK but might have outsiders reaching for the urban dictionary every few minutes. Other than that, I have no hesitation recommending Rivers of London. The fact that I've already launched into the sequel within a minute of finishing it says something about its appeal.