From the back cover:
UNLEASH THE HORRORS OF THE VICTORIAN NIGHT!
Reveal sinister secrets, forbidden lore, and mysteries of the late 19th century at your gaming table.
Cthulhu by Gaslight takes the Call of Cthulhu roleplaying game to the fog-shrouded streets of London and beyond. This book is specifically for Keepers—those who will be running the game. Inside, you'll find:
Advice for bringing the late-Victorian setting to life.
Villainous organizations and occult societies like the Hermetic Order of the Golden Dawn.
New occult-based skills, spells, tomes, and rules for astral combat.
Two introductory scenarios.
Monsters and the Cthulhu Mythos in Gaslight Britain.
Scenario seeds to help you create Gaslight stories of your own design.
This book requires the core rules found in the Cthulhu by Gaslight: Investigators' Guide, available separately.
Enhance your Cthulhu by Gaslight experience with the Call of Cthulhu roleplaying game and the Pulp Cthulhu supplement, both available separately.