Castle is an author of mystery fiction, with 26 bestsellers. His first novel, "In a Hail of Bullets", accrued at least 21 rejections before being accepted by a publisher (he keeps the first rejection letter he received framed on his office wall as motivation) and winning the Nom DePlume Society's Tom Straw Award for Mystery Literature. The books have made Castle wealthy; when Alexis is kidnapped he can pay a $3 million ransom. Castle has a large multi-floor Manhattan apartment, a beachfront house in the Hamptons, and luxury cars.