This book is far beyond the usual one-shot adventure for Trail of Cthulhu. The book provides an entire campaign setting set in London during the standard 20's/30's Lovecraftian time period. The cool part is that you aren't necessarily an investigator of creepy paranormal activities. You are a collector of rare books, which often happen to discuss rituals, truths, and mysteries that are better left buried in the annuls of time. As you try to buy and sell these books, you are invariably pulled into terrifying situations that will test your sanity.
The book includes character suggestions and motivations, extremely detailed maps of London at the time, rules for upgrading and managing your shop, and of course story hooks for adventures. This is an amazing resource that you can read almost like a novel even if you aren't planning on running the game. If you are interested, this is for a more advanced player as the history is pretty deep. However, use what you want and roll with it if you are a novice. This is a great setting that can be used to really play into the everyman pulled into extraordinary scenarios in a Cthulhu setting. Love it.
[5 of 5 Stars!]