SQUARE'S PROGRESS by Wilfrid Sheed. 309 pages. Farrar, Straus & Giroux. $4.95.
"You're not really very interesting, Fred," muses his waspish wife. "Take away the eyebrows and what have you got?" What you have is a lumbering, complacent insurance salesman of 27 who likes baseball, television, Peanuts, sex and practically everybody he knows. He is too unendurably dull for Wife Alison, a nattering know-it-all who reads Proust and thinks life should be lived as a work of art. She leaves him, goes back to Stapleton, Pa. Shocked into action, Fred quits his job and solemnly sets out to discover how to be...