The Pawns of Null-A

From the back cover of the Ace first edition: "The galaxy was their playing field, the universe their prize! - Gilbert Gosseyn, the null-A genius of the Earth-Venus war, never realized that this interplanetary struggle was but a border incident in a greater conflict until he was thrust onto the galactic battlefield as a mere pawn. But in picking Gosseyn as "expendable," those cosmic opponents unleashed forces they had never dreamed existed. One was the entrance of a powerful third party in the war. The second was the ability of certain other pawns to foresee the future. Finally, there was the secret of Gosseyn's original purpose - a secret which could decide the fate of the entire Galaxy!"