Just as E. M. Forster's novel of gay love, Maurice, remained unpublished throughout his lifetime, Glenway Wescott's long story "A Visit to Priapus" was also destined to be a posthumous work, buried from 1938 until this century in Wescott's massive archive of manuscripts, journals, notebooks, and letters.             The autobiographical story is about a literary man, frustrated in love, who puts aside his pride and makes a date with a young artist in Maine. Lavishly rendered in Wescott's elegant prose, the tale is explicit where it needs to be, but--as is typical of Wescott--it is filled with descriptive beauty and introspective lessons about sex and sexuality, love and creativity.             Previously published in anthology form in the United Kingdom, "A Visit to Priapus" is presented for the first time in book form in America, containing previously uncollected stories, including three never before published. The result is a candid portrayal of the gifted but enigmatic writer who was famous in youth and remained a perceptive and compassionate voice throughout his long life. Drawn together from midcentury literary journals and magazines of the 1920s and 1930s, as well as from Wescott's papers, the stories were inspired by his life, from childhood to old age, from Wisconsin farm country to New York, London, Germany, and Paris. Finalist, Gay General Fiction, Lambda Literary Awards