This is the very first version of Dungeons & Dragons as a complete game, which had several printings up until November 1975. The three books inside were Men and Magic, Monsters and Treasures and The Underworld and Wilderness Adventures. It contained references to 'Hobbits' and 'Ents' which were eventually replaced by 'Halflings' and 'Treants' at the insistence of the Tolkein estate.
More when I get hold of a copy!
Book Details:
Authors: Gery Gygax and Dave Arneson
Publishers' Reference: TSR2001
ISBN: Unknown
Box set, 3 books
Date: 1974
Product page last updated: 23 June 2014