4.5 stars. I really liked the book and the world. I agree that the blurb is misleading. Sean and Mendel are not the main characters. Rather, we spend more time with Cyan and Einn. The cover photo also leads you to expect a more lurid story than you get. What we do get is a very enjoyable sci-fi story, with dozens of different races and planets, a lot of cool world building on the politics and special powers of the creatures, and a very lovable pair in Cyan and Einn.
As always, I wouldn't have minded more sex/kink, but what was there was very well-done. I also have to give special praise for the villain. In most books, the villain is just so perfunctory, but Jade was really fun--he also seemed like the most motivated and clever of the characters (in addition to obviously being the most fashionable!) I really like stories where the energy levels go up whenever the villain is on stage--this was one of those.