The Magic Labyrinth (The Riverworld series ; v. 4)

The answers behind the enigmatic origins of Riverworld lie at last within reach, as the remarkable gathering of Earthlings--including Sir Richard Francis Burton, Samuel Clemens, Alice Liddell Hargreaves (the real-life Alice in Wonderland), Cyrano de Bergerac, Ulysses S. Grant, and Baron Von Richtoven--finally breaches the stronghold of Riverworld's extraordinary super-race.
But answers would lead to more enigmatic questions . . .
Who is the Mysterious Stranger who taunted the Riverworld resurrectees with hints of the truth? What is the key to the gargantuan computer that wields the power of life and death? The astonishing secrets lie within the Dark Tower--but only for those brave enough to seek them and wise enough to decipher them . . .