3.5 stars. Many interesting ideas here, some explored well, some barely mentioned, and a fast-moving plot that makes this an easy read, but let down by its age. This book was clearly written when sci-fi was for boys, and women were auxiliary characters who must be described and valued solely by their appearance. That got pretty wearing. There's also a scene (I didn't go back to check, so maybe it's "technically not") that is basically rape. Cool.

Once the women disappear and the book busies itself with the world itself, things get a little better (I know, sorry). Riverworld, where all the humans of the past and present have been reincarnated and made to live together, lets the author explore conflict, language, nudity and base desires, the ethics of reincarnation, whether we should give war criminals second chances, and what to do to occupy one's self in a post-work world where all the necessities are provided. (The author's answer — war! It keeps things from getting too boring! Yeesh.) I liked these ideas but would happily have seen them explored with more depth.

Overall, I enjoyed it in a kind of pulpy way, but I won't continue reading the series.