Catarina von Hasenberg is used to being underestimated. In fact, given the powerful world within which she operates, she encourages it. Her family is one of the most powerful ones in the universe and thus have some pretty powerful enemies. A fact that became all two clear in the first two books of this Consortium Rebellion trilogy. Cat's problem right now is that she may have done too good a job convincing people that she's just a flighty socialite. So much so that not even her family thinks she can help in waging the battles they face.
But she has a plan to change all that.
Cat has finagled an invitation to a house party being held at the home of a rival family (one that she thinks may be responsible for an attack on her brother). If she can get into the house, she'll be able to search for proof of their treachery. All well and good. But her overprotective sister requires that she have hand-picked bodyguards, one of whom, Alexander Sterling, will pose as her partner (thus being able to remain close to Cat at all times). Though Cat is sure she can do the job without help, she agrees to the plan. When events spiral out of control and reveal a much bigger world-changing plot, Cat is glad to have Alex's help.
If you're looking for the same romantic zing that the first and second books in this series provided (Polaris Rising and Aurora Blazing), you won't find it. Alex as a character and romantic lead was never developed beyond Cat liking him and his being an honorable guy. He's kind of just there. But as an SF action story, this one hit all the right notes. And the characterizations of Cat and her family members helped to ground a complicated political plot. I look forward to what the author does next.