The Dark Design(Riverworld‪)‬

Years have passed on Riverworld. Entire nations have risen, and savage wars have been fought—all since the dead of Earth found themselves resurrected in their magnificent new homeworld. Yet the truth about the Ethicals, the powerful engineers of this mysterious "afterlife," remains unknown. But a curious cross-section of humanity is determined to change that situation … at any cost.
Intrepid explorer Sir Richard Francis Burton leads the most remarkable voyage of discovery he has ever undertaken. Hot on his heels are Samuel Clemens, King John of England, and Cyrano de Bergerac. Spurred by the promise of ultimate answers, they chart a course across the vast polar sea—and toward the awesome tower that looms above it. But getting there will be more than half the battle. For death on Riverworld has become chillingly final …