Parodists have a tremendous advantage over ordinary run of the mill humor writers. People will laugh at their stuff even if it is only vaguely good, so long as they feel at least two jumps ahead of the parodee.

Yet there is one parodist who seldom needs to wield this club over a self-anesthetized audience. Ira Wallach, who proved his wit in his "Hopalong Freud" series, has a new book, called "Gutenberg's Folly."

Subtitled "The Literary Debris of Mitchel Hackney," Wallach's new one is especially funny because of its novel gimmick. Hackney, says Wallach, is one of the great unsung literati of our era, great because he managed to do everything years before it was done by the person we credit with doing it. Hackney, for instance, out Saroyaned Saroyan and out-Bellowed Saul Bellow, and did it first. "Gutenberg's Folly" is therefore a labor of love: dying from a surfeit of chopped liver canapes, Hackney willed Wallach his wife and his work.

The book is so consistently funny that it is hard to pick a "best." But if such a choice must be made, I'll place my money on "A Practical Guide to the Fat Life," which neatly hangs a literary tin can on Norman Vincent Peale. In describing his spiritual counsel to a would-be business executive, Hackney says, "I took his hand and led him toward the analyst in the vestry room. 'The raccoon,' I continued, 'always washes his food before eating. Why not 'raccoon' your mind?... Since then that young man has risen from envelope-sealer for Eastern Steel to the ownership of one of the largest clip joints in Las Vegas! And why? Because he learned to 'raccoon' his mind."

In "The Pilgrimage of Bixie Davis," Wallach takes a cut at the picaresque, naturalistic novel as typified by Bellow's "The Adventures of Augie March." "Lilian was pliant and I molded her. Her love and muscle, tore through the Grand Central Station of my mind to the Chicago of my belly. What for myself did I out of all this want?... Then she rose, Cleopatra-thighed but unasped, and went to her room where she Godiva'd, belly-bundled, a Marie Antoinette with a bagel."

Everything from Eliot's "Ash Wednesday" to New Criticism and beer testimonials by famous authors receives the Wallach treatment, and usually emerges the better for it. Richard H. Ullman