The second book in Farmer's imaginative Riverworld series is better written although the plotting can occasionally still be a bit haphazard. Like To Your Scattered Bodies Go, Riverboat was originally serialized prior to publication. Despite some rewriting by Farmer, the second novel's pacing is inconsistent. The characters, like the first novel, are interesting and imaginatively portrayed. A fair warning, however, since most of these characters are from the 19 or early 20th Centuries, they aren't the most enlightened males. There's a hint of misogny and sexism at the core of many of these characters. I don't believe that reflects Farmer's point of view. Instead, it reflects the attitude and era of the male characters. What compounds this minor flaw, though, is the fact that Farmer couldn't convincingly write a strong female character(a problem that dogged the first novel). Here he primarily sticks to the male characters and the novel benefits from it.
Sam Clemens (aka Mark Twain), like Richard Burton, is intent on discovering the source of the great river and identifying the people who resurrected humanity. His companions include Joe Miller a brutish prehuman giant who, surprisingly, shows more humanity than most of Clemens' friends; World War 1 flying ace Von Richthofen who provides a sense of balance to Clemens' dark view of humanity and Erik Bloodaxe a harsh and cruel viking that is has Clemens as a member of his crew chiefly because Clemens claims to know a source for iron.
Clemens goal is to build a marvelous riverboat that will help him achieve his goal of discovering the motives of X the mysterious stranger who appears out of nowhere to help him (just as he did Burton) in his quest and why they've all been returned to life.
A couple of points--1) Keep in mind that this was written in the late 60's and published as a novel in 1971. It's of its era but the writing and themes have aged surprisingly well. 2) Although it wasn't designed with adolescent males in mind necessarily, that was the primary audience for the original piece. The attitudes and writing style occasionally demonstrates these elements.
Regardless, this is a fun series and still highly regarded for a number of good reasons. Farmer's novels and his ability with female characters would improve with later installments. By the time of the third volume The Dark Design, most of the flaws that dogged the first two installments had been overcome. The Riverworld series is still a well written series. While the series lost much of its power by the fifth and final book, there were still enough ideas floating around in one book that a lesser novelist would have made into 10 or 20 novels. In the series driven novels that have overtaken the science fiction genre, Farmer's novels, like Frank Herbert's, were written out of a love for the material not out of commerce. This attitude prevails even in the lesser books of this interesting and engaging series.
My only complaint with the latest editions are no comments or observations by Farmer 30 years after their initial publication. When these were first published (in 1998) Farmer was still going strong and working on a number of new novels and projects. On a side note it's a pity that the Science Fiction Channel ruined the first adaption of Farmer's novels. Riverworld was a mess where Burton was replaced by a 21st Century astronaut (obviously those teenagers wouldn't be able to relate to someone as obscure as Sir Richard Francis Burton!). It was a horror unlike the adaption of Herbert's first three novels.