Books like The Magic Labyrinth

At the end of The Fabulous Riverboat, Sam Clemens finally set out in the great iron riverboat Not for Hire to reach the headwaters of the massive river on whose shores humanity has been resurrected. After 33 years on the river, Clemens and his crew--including the giant subhuman Joe Miller--are finally near the end of their journey, and only one obstacle remains: the evil Earthly king, John Lackland. John is waiting just upriver in the Rex Grandissimus, the first riverboat that Sam constructed and the one that John and his crew hijacked, and he's hell-bent on sinking Sam's boat (and vice versa). Complicating the battle is the fact that both ships likely contain agents of the Ethicals, the group of advanced beings who created Riverworld for reasons unknown. One or more of the Ethicals themselves may even be on board, as are various humans that the rebel Ethical, known as the Mysterious Stranger (but known to Clemens simply as X), enlisted in his cause, which may or may not lead to humanity's salvation. The battle is set to take place along the shores populated by members of the Church of the Second Chance, a group that believes they must attain ethical perfection in order to proceed to the next phase of existence. The Second Chancers are not violent, but their charismatic leader, La Viro, may attempt to sink one or both of the iron ships in order to prevent the battle. Among the Second Chancers is former Nazi officer Hermann Goring, who had a run-in with Sir Richard Francis Burton in the first Riverworld novel, To Your Scattered Bodies Go. Burton and his companions--among them several people who were contacted by the Mysterious Stranger--are reluctantly serving on John's boat in order to reach the headwaters of the river. But will any of the humans working for X survive the coming battle? And if so, how can they possibly hope to penetrate the tower in the North Sea where the Ethicals are thought to reside? And what could lowly humans hope to do against a race so advanced that they can reshape entire planets and resurrect all of humanity? --Craig E. Engler