Bookhounds of London is a Trail of Cthulhu supplement that puts the players in the role of a bookseller of strange and occult tomes. The generic hook is that the quest for forbidden knowledge can drive a lot of mythos stories. The supplement describes how the odd booksellers market works in London. Booksellers range from the odd pushcart to wealthy established shops.
I got a lot of inspiration on designing or modifying Call of Cthulhu scenarios from this book. The quest for forbidden knowledge and the characters surrounding that market is a wonderful idea.
I have my doubts about the usefulness of running a campaign where characters run an occult bookstore. It is a fine idea, but a book length setting for this is too much. You have to sell books to make money to keep your shop open in the 1930s, but some books are horrible and should be burned. Balancing the two would be challenging. The entire setting is very London-Centric which could be an excellent or poor idea depending on the GM.
There is a scenario included in the book that did not seem to be that fun for players. It revolved around several people trying to obtain a book and their movement towards a sale or auction. There was not a whole lot of action and even the scenario author described the frustration felt by playtesters.
In sum, as a book to generate inspiration for designing Cthulhu or occult scenarios I think it is excellent. To center a campaign where everyone is in the book industry - I have my doubts. The scenario itself seemed uninteresting and potentially frustrating for players.
[4 of 5 Stars!]