The Book of the Smoke is an oddity. The intentional use would be as an in-game prop for any setting where an occult London would be researched; however, it is best suited for Trail of Cthulhu, particularly the Bookhounds of London (a great read, by the way).
The text itself is a look at London’s occult scene. It is separated by places and persons. The majority of the book deals with places for investigators to, well, investigate. This is the genius of the book.
With a style similar to one found in a folklore journal, the author lays out rumored locales of high strangeness. These places, seeds really, are left wide open for clever keepers to nurture into something else.
The best part: After an investigation check, the Keeper can hand a tattered page or two from the book as a clue for the players to take in. They can make what they will of the academic, somewhat biased text. Since it’s a text clue, the Keeper can save his poker face for bigger moments in the game.
And it keeps in flavor with the game.
Some figures are well-known (Aleister Crowley, for example); others are not. The author does well making the read sound authentic. It’s “written” by a contemporary of the occult movers and shakers and it reads like it.
Overall, The Book of the Smoke feels like an extremely focused product, which is a disservice to it. There is a great deal that can be mined from this book, but it’s not as readily available (or advertised) as that. If you’re a fan of supernatural horror, take the time to check out this read. It’s system neutral, but tied to the late 1800s and 1900s (some times vary, but the majority fall there).