British novelist Robert Harris, whose latest, Pompeii, is a bestseller for Random House, is moving to Simon & Schuster/Pocket Books in a huge three-book deal. S&S publisher David Rosenthal, who signed the contract for U.S. rights with agent Michael Carlisle, said the first of the new titles, to appear in fall next year, will be a novel of politics in ancient Rome, the first of a trilogy. Harris, who was originally edited by Rosenthal at Random House, said it would be his most ambitious project so far. He is a former BBC correspondent whose bestsellers include Fatherland, Enigma and Archangel.