This was a phenomenal story. It's hard to call it sci-fi because it's not set in space, but the alien technology aspect of it still gives it that feel even though it's set on modern-day Earth. 
 So, aliens crash land on earth near a military exercise. The US military finds a crashed alien spacecraft and maybe 8 alien survivors. Unfortunately, someone with an itchy trigger-finger escalates the situation until there are casualties on both sides and all of the aliens are dead. Or so they thought. While transporting the bodies back to a military base (no, not Area 51/Roswell), one of the AI armor/weapon systems escapes and manages to catch a ride with one Riley Cooper. 
 Riley is already on the run from his ex-boyfriend, Misha, who is currently a Russian mafia sicario (hitman), and who kept that information from Riley. To be fair, Riley willingly blinded himself to the signs until he couldn't any longer. He's been on the run 2 months and then sees a familiar face in the crowd, and he ups and runs again, this time crossing paths with something entirely unexpected. 
 Desperate to find a host because he'll soon disintegrage, the system invades Riley by force, though he is apologetic about it. Thus begins Riley's attempts to become accustomed to and get rid of the alien hitchhiker while also trying to evade his ex's tracker. And the alien intelligence decides to name himself McClane after the character from the Die Hard movies. 
 Everything comes to a head in El Paso, TX when the military AND the ex catch up to him. 
 There were several moving pieces in this story. It's told in 3rd person omniscient, so we see all the events from all sides. We meet the Special Operations Commander who is tasked with bringing back the alien, alive if possible, dead if not. And the military doctor who did the autopsies of the alien bodies and determined part of the nature of the armor. We meet Misha's sister, Mariya, who is determined to have more control of the family business than a woman will ever be allowed, and who loves her brother and doesn't want to kill him to make that happen. We meet Misha and his associates, who are trying to keep him and Riley alive. And of course we meet Riley and McClane, who have to learn how to cooperate in one body if they have any hope of making it out of this situation in one piece. 
 McClane is certainly a character in his own right. He is sentient, even though he cannot exist outside of a host body. He and Riley talk back and forth in Riley's head, though Riley has the cute if annoying habit of speaking aloud to McClane because thinking at him makes Riley feel even more insane. He has opinions and free will, though he likes Riley and chooses not to force his will even when the situation seems to call for more violence than Riley is willing to use. 
 This is definitely a menage story in that sense. And yeah, it's rather hot and intense at that, at least for Riley, who feels it inside and out. 
 The story was just a touch slow in the middle while all of the pieces are figuring out their next move, ultimately coming together at a small diner in El Paso. But it was barely noticeable because the story was a very compelling read. I'm not sure I completely bought into the ending, but it was good enough that I'm not going to pick it apart. And I can easily see this carrying into a series if the author desires. 
 A very satisfying read, and a highly recommended action story to rival Zero at the Bone, but with an alien twist.