From the back of the book:
OGL Horror is your key to the hidden world of terror that lurks behind reality’s paperthin walls. Whether you are trapped in a world full of zombies, walking alone in a haunted house or hunting the most twisted serial killer ever created, OGL Horror sets the scene and paints the black mood.
This core rulebook, published under the Open Game License, contains everything a brave victim could require; from full character creation and roleplaying rules to an armoury of chainsaws, stakes and nailguns.
TURNING THE SCREW: Expert advice and rules for players of any experience on how to create the horror mood and send shivers down the hardiest spine, plus full systems for magic, psychics and the power of faith in a reality that is tearing open at the seams.
WORLDS OF HORROR: OGL Horror provides a bulging, bloody bag of tools for all scenarios, from sample campaigns to a chilling bestiary, detailed psychology and insanity guides to making your own personal conspiracy.
Just remember - save the last bullet for yourself.