If you'd like to read a series that combines science fiction with mystery and thriller elements, try Kristine Kathryn Rusch's Retrieval Artist series, starting with The Disappeared. It's about a man who starts out as a police officer on the Luna Colony, whose duties are about to force him to hunt down humans who have inadvertently committed crimes against alien cultures and who have been sentenced to various horrible fates. He doesn't like doing this, and all sorts of startling developments ensue. There are seven in the series so far, and they're all consistently good.