If you hear that Larry Gonick is a Harvard Ph.D. laboring on a projected four- volume history of the world, you may think this is a reading experience that's a lot tougher than you'd care to attempt or read. But get a load of the freshly published The Cartoon History of the Universe II (Doubleday, $15.95): It's world history as an educating riot. Gonick is a professor who's also a first-rate cartoonist; the first edition of The Cartoon History, published in 1990, sold over 100,000 copies and won praise from folks ranging from Carl Sagan to Ann Landers. This second volume begins with ancient India and moves on through the fall of the Roman empire, concluding around the year 600. Drawn with painstaking geographical detail but populated by wisecracking cartoon characters, this History guides you through Chinese philosophy, Babylonian hugger-mugger, and the murk of the Dark Ages. There is even a cartoon bibliography at the end of the book. A work of scholarship and looniness, The Cartoon History is a valuable document in its own right.