The third book in Philip Jose Farmer's Riverworld series The Dark Design differs in several ways from its predecessors.
First, it is almost three times as long. Yet, it is only the first part of a two-book conclusion of the plot started in the first two novels To Your Scattered Bodies Go and The Fabulous Riverboat. A conclusion that will be over 400.000 words long as Farmer himself reveals in The Dark Design's introduction.
Second, while the two predecessors are self-contained The Dark Design builds on characters and plot lines introduced earlier. To fully enjoy it you have to know the other two novels.
Third, Farmer wants to further develop most of his main characters leading to several changes in the narrative perspective. He switches back and forth the different plot lines. Sometimes he describes the same events from the viewpoint of two different persons thus connecting to two strands of his story. Sometimes he changes abruptly place and persons.
And finally, owing to the circumstance that the series has a two part conclusion the book ends with a cliff hanger, forcing the reader to start reading the last volume if he wants to know the answers to all the questions he has after finishing this tome. And the last few pages raise more questions than the preceding several hundred pages (try to) answer.
The Dark Design is still quite enjoyable. Though I did not like the regular changes in perspectives. Farmer easily could have split this book in 3 separate novels and thus stick closer to the style of the first two volumes. On the other hand, I never complaint about Jordan's The Wheel of Time, so why start nagging here?