Neptune City - Humorist Jean Shepherd stood in the Gallery East Book and Art Shop yesterday signing copies of his new book, "Wanda Hickey's Night of Golden Memories and Other Disasters," and he talked effortlessly in the same manner that he conducts his late-night radio show. At one point he described himself as an "inveterate liar." The popular master of monologue was greeted by a store full of admirers, who stood in line with newly purchased copies of Mr. Shepherd's latest book or editions of his earlier books, "ln God We Trust, All Others Pay Cash" and "The America of George Ade." Before autographing books, Mr. Shepherd answered questions from those present, explaining that the book took more than three years to write and that the characters and places are composites of many persons and places he knows well. Mr. Shepherd's mood was light and when asked whether he knew the difference between Neptune and Neptune City he said, "l imagine there's a vast philosophical difference." He was questioned about how factual his stories of life in the Army and back home in Indiana really are and quipped. "I'm an inveterate liar. My mother thinks I'm in insurance in New York." Mr. Shepherd has completed a season on educational television which brought favorable comments from those present, and many longstanding admirers complimented Mr. Shepherd on his WOR radio shows of several years ago from the Limelight in Greenwich Village. His style is to deliver a loosely knit monologue in which he plays all of the characters in various situations supposedly from his own past. Michael Stern, manager of the book store on 3rd Ave., said the owners invited Mr. Shepherd to come here through the assistance of Doubleday Publishers, which released "Wanda Hickey 's Night of Golden Memories" Friday. The book Is Jean Shepherd's first since 1966, when "In God We Trust," was published. The writer and radio personality will appear today at the Red Bank Book Store, 6 Linden Place, from 1 to 3pm.