Farmer's Riverworld series (To Your Scattered Bodies Go; The Fabulous River-boat) may come to an end some day, but at one point in the present installment the figure of twelve is mentioned as the minimum number of books necessary to do justice to the whole scheme. Oh, dear. Certainly the premise is an infinitely usable one: practically every human being born between 2,000,000 B.C. and 2008 A.D. has reawakened as a healthy 25-year-old on an unknown planet' that appears to consist of one enormous, tortuous river valley walled by impassable cliffs. The present volume continues the Riverworlders' efforts to conquer the benevolent (or perhaps not so benevolent) prison of the River and the valley. Sam Clemens is still commanding his second riverboat and plotting revenge on King John, who stole the first. A dirigible party including Cyrano de Bergerac is planning an expedition to the legendary stronghold of the planet's unseen masters at the North Pole. Another riverboat crew, headed by Jack London and Tom Mix under noms de guerre, manages to graduate to balloon flight. A few select individuals ponder a mysterious communication to the effect that the entire Riverworld is part of a cruel and cynical scientific experiment. Is it possible that such materials could be boring? Yes, given Farmer's shaky command of English grammar, tin ear for stylistic effects, and general insensitivity to the shape of a narrative. Enough already.