From the publisher's website:
Dark Heresy Second Edition is a roleplaying game of danger, mystery, and brutal violence set in the decaying far future of Warhammer 40,000. Players take on the role of defenders of humanity and embark on hazardous adventures into the dark heart of the 41st Millennium. As an Acolyte of an Inquisitor, you’ll serve at the front line of a great and secret war to root out dangers that imperil all of humanity.
The 448-page, full-color Dark Heresy Second Edition Core Rulebook contains everything you and your friends will need to serve the Emperor in the Askellon Sector. Rules for character creation, combat, and adversaries are supplemented by informational source materials that will help Game Masters bring the Askellon Sector and its horrors to life. The Dark Heresy Second Edition Core Rulebook can be used to enjoy standalone adventures and ongoing campaigns in the grim future of the 41st millennium.