While it's not a two-player "choose your own adventure" book, but more of a two-player "Fighting Fantasy" book, the Duelmasters book Challenge of the Magi is quite similar. In it the players take the role of two wizards facing off in a duel-to-the-death across the planes.
All it requires is a die, and pen and paper to record items, spells, hitpoints and codewords.
I loved this pair of books as a kid, which can be testified to by the fact that my two books are literally falling apart at the spine. The books also contains guidelines for playing it single player.
Similar in some regards to the Ace of Aces book series, Duel Master takes 2 players, each with their own book, into competition with one another. Play is paragraph based, with each player making their own choices about what they want their character to do.
In "The Challenge of the Magi", each player takes on the role of a mage (specializing in one of five types or colors of magic), putting themselves forward as replacement for the recently deceased head of the council. Who shall rule is determined by ritual duel to the death in the Rainbow Land - a series of interconnected dimensions, each filled with its own denizens and incorporating its own magical laws.
There is apparently a whole series of these books (the Duelmaster series), which I have heard are all quite differnt to each other, but I have never managed to find a second one.
Having a look on BGG, there appear to be a few more:
- Blood Valley, one player is a demonic hunter, the other is his prey.
- The Shattered Realm, each player is the leader of a kingdom, building up allies for a showdown between the two.
- Arena of Death, players are both gladiators in the arena.