"... arise From death, you numberless infinities of souls, and to your scattered bodies go..." -- John Donne.

Philip Jose Farmer

Not only has Farmer been responsible for the Riverworld series, but he is perhaps best known for his World of Tiers cycle.  His fascination for history and the characters who make it led him to explore his boyhood heroes in a universe of his unique creation.  

An excellent site with all the info on Farmer you could want is The Official Philip Jose Farmer Homepage.