Is there an American novelist who has fallen farther from grace than John P. Marquand? For years he was one of the best-known names on the bestseller lists, and his part-time job as a judge for the Book-of-the-Month Club made him as influential as he was successful. But Marquand wasn’t a hit with the highbrows. Edmund Wilson, writing in The New Yorker in 1942, went so far as to declare that “Mr. Marquand hasn’t the literary vocation.” Marquand was stung by such sniping, and despite his Pulitzer Prize and Time cover, he went to his grave sure that he’d gotten …