In addition to being the author of The Story of My Baldness, Marek van der Jagt is its narrator. Also, he does not exist. The best-selling Dutch novelist Arnon Grunberg, acting with a prankishness variously clever and empty, has invented Marek, a droopy philosophy student in Vienna, in the service of a loose, mildly surreal anti-coming-of-age tale (supposedly translated by one ''Dr. Todd Armstrong''). The hero's obsession, sexually and intellectually, is mad love. ''L'amour fou was a little like the flames of purgatory,'' he proclaims. ''You had to be consumed in order to emerge purified.'' Marek's voice, at once clinical and adolescent, is what gives his romantic misadventures (first kiss, deflowering, anxiety about physical endowment) their fun air of droll farce.