From the publisher's website:
CALL OF CTHULHU is Chaosium's classic roleplaying game of Lovecraftian horror in which ordinary people are confronted by the terrifying and alien forces of the Cthulhu Mythos. CALL OF CTHULHU uses Chaosium's Basic Roleplaying System, easy to learn and quick to play. This bestseller has won dozens of game-industry awards and is a member of the Academy of Adventure Game Design Hall of Fame. In 2001 CALL OF CTHULHU celebrated its 20th anniversary. In 2003 CALL OF CTHULHU was voted the #1 Gothic/Horror RPG of all time by the Gaming Report.com community. CALL OF CTHULHU is well-supported by an ever-growing line of high quality game supplements. This is the softcover 6th edition of this classic horror game, completely compatible with all of previous editions and supplements for CALL OF CTHULHU. This is a complete roleplaying game in one volume. All you need to play is this book, some dice, imagination, and your friends.
20th anniversary, Contributors edition: there are only 50 of them each signed with the name of a GOO
Great Old One / Cthulhu deity