The "original" Dungeons & Dragons created by master magicians Gary Gygax and Dave Arneson. It was published in 1974 and is a bit of a far cry from the D&D that was yet to come. But it's amazing to see this early take on the rules.
There were just three classes included: Fighting Man, Magic User and Cleric. Four races: Human, Elf, Hobbit and Dwarf.
The game was based on the miniatures wargame Chainmail and it borrows heavily from those rules.
Rules for Fantastic Medieval Wargames
Campaigns Playable with Paper and Pencil
and Miniature Figures
The set includes :
Volume 1 : Men and Magic
Volume 2 : Monsters and Treasure
Volume 3 : The Underworld & Wilderness Adventures