From the back of the book:
DUNGEONS & DRAGONS fantasy game is a step out of the ordinary. Each adventure is like writing a novel. Players assume the roles of elves, dwarves, halflings, or humans and travel through a fantastic world filled with danger and excitement. Adventurers will wander through frightening dungeons conquering evil foes and meeting terrible dragons.
DUNGEONS & DRAGONS fantasy game is the original "role playing" game and this booklet makes it easier than ever to play. This rulebook contains all the rules needed to begin playing and running DUNGEONS & DRAGONS adventures. The rules have been reedited and organized so that people who have never played the game before will be able to begin playing with a minimum amount of preparation. DUNGEONS & DRAGONS fantasy game can be played by anyone. The entire family will enjoy a DUNGEONS & DRAGONS adventure. And with the more than 100 monsters included in this booklet no two adventures will ever be alike.
This rulebook was sold separately, as well as being part of the Dungeons & Dragons Basic Set (Second Edition) set. A PDF version of this rulebook is also available.