Unearthed Arcana (1985)

From the web:

This tome, for players of the AD&D game, contains much information that has never before been published. It is an excellent resource for intermediate and advanced players and Dungeon Masters, ages 10 and up.

All the new discoveries, plus a wealth of just uncovered secrets, between one pair of covers. Unearthed Arcana further defines and describes the game system. Inside are new spells, character classes, magic items, weapons, and much more for both players and Dungeon Masters. 

From the back of the book:

This, the latest of the AD&D game books, further defines and describes the game system. Inside are new spells, character classes, magic items, weapons, and much more for both players and Dungeon Masters.