(I got an e-copy through NetGalley, in exchange for an honest review.)
A fast and interesting read, with plenty of little details and usually unknown facts about quite a few places in London. As someone who's visited this city a couple of times only, but likes learning about it, and is always looking for a "quirkier" kind of tourism than the basic monuments and museums, this is definitely going to be useful at some point. Another good thing here is the author's tone, who clearly loves this city, as well, and it shows (in a positive way, that is).
The book might not hold as much appeal to a reader who's never foot in London, though, because it rests on unspoken previous spoken knowledge of the various districts: some details can only be fully understood when you know a bit about this or that borough, how it came to be, and so on. I wouldn't recommend it as a "London 101" introduction book.
Also, I would've liked a few more pictures. There's usually one per chapter, while said chapters deal with so many more places than just a couple. (Granted, I read it on the Kindle app on my small-screen Smartphone; not the smartest move ever—no pun intended.)
Pick this one if you're planning a trip to London, want to discover more about its history, and are interested in seeing less travelled places there.