Extremes is the sequel to Rusch's The Disappeared. Like the original novel, the sequel blends speculative fiction with a police procedural, detective storyline.
However, unlike the first Retrieval Artist novel, there are no aliens; the events and plot are tightly contained around an all human cast and a murder investigation at the annual Moon Marathon.
Overall, the novel is weaker than The Disappeared: the lack of aliens and inter-species cultural conflict bleed the speculative world of some of the verisimilitude Rusch crafted in the introductory novel, and Miles and some of the other characters seem a little too contrived.
Still, as with all Rusch novels, the writing is so good that it is transparent and the experience of reading her prose is light and relaxing. So, I would recommend Extremes to dedicated Rusch fans or those readers interested in a fast, well-written but at times contrived speculative novel.