The Chessmen of Mars by Edgar Rice Burroughs

The fifth book in the popular Barsoom series, The Chessmen of Mars is a 1922 science fiction novel by Edgar Rice Burroughs. Tara, princess of the great city state of Helium, is initially impervious to the courtship attempts of Gahan, prince of the city state Gathol. But when she loses control of her craft in a storm and is captured by the Kaldanes, horrific crab-like creatures who've sacrificed their bodies in the pursuit of intellect, the deeply smitten Gahan sets out to rescue his princess and prove his worth. But this is a challenge that may forfeit his life and hers, as he and his companions are forced to become pawns in a game of Jetan, Barsoomian Chess on a life-size board that uses the living as its pieces and the dead as its conquests.