Read: Gods of Riverworld
This is it: The final Riverworld novel. Though the novel ends with the proclamation of a new adventure, providing every possibility for a sequel, there will not be any Riverworld sequels by Philip José Farmer. He died earlier this year.
Yet, already Gods of Riverworld is not really a Riverworld novel any more. The story does not take place on the River. The whole plot proceeds within the Tower at the headwaters. Here, the new occupants have almost god-like powers provided by the vastly advanced technology. And they us their powers to build their own private little worlds and raise their favorite companions from the temporarily without-a-living-body.
This gives ample room for a deeper look into the psyche of Farmer's protagonists instead of the cursorily glance at their characters he provided in the immediate prequel. There is plenty of action and a few surprises.
At the end, Farmer even frees himself from the esoteric / mystic / religious connotations of his earlier Riverworld novels. Or does he? Nevertheless, this results in an interesting development of the whole series on several levels: The technological (from stone age, steam punk like technology to advanced futuristic technology including FTL), the societal and religious, and, of course, his literary characters. I liked the creative use of historical figures. At least I liked it most of the time… Let's see how much I will like Farmer's other series, The World of Tiers.