Double Game: The Glade of Dreams

The "Double Game" series of books uses a combat and inventory system familiar to many "fighting fantasy" style books. But this one allows two players to play simultaneously (each using a different book of the pair). The books use cross-reference tables to allow the players to interact with each other (usually cooperating) at certain points. One player player plays Darian, the Master Magician. The other plays the Issel, the Warrior King.