A Clash of Kings
Though first mentioned in 1996's "A Game of Thrones", Stannis formally appeared in "A Clash of Kings" (1998), "A Storm of Swords" (2000) and "A Dance with Dragons" (2011). In December 2011, Martin posted a sample chapter from the yet-unfinished "The Winds of Winter", told from Theon Greyjoy's viewpoint, which confirmed Stannis' return in the sixth book.