Good and entertaining, but it could have been freaking awesome.
I'm actually a bit disappointed because there was so much potential here. Dark and scary and kicking assery awesome. Unfortunately, it falls into some well-trodden tropes that a 'mean' editor or beta reader should have red-lined. I mean really, evil secret government military experiments?
This is a romance. Terrific, but for all that is holy! stop with the repetitive, 'oh, he's hawt', 'oh, he's so sexy, what a fine ass', 'wow, what an ass'. I got it the first time, now would your TSTL ass of a heroine just STFU and go kill some zombies?
The heroine. Yeah, the more I read of her, the less I liked her. She just does some really, stupid things including a really TSTL moment when she goes off to 'check' a hallway WHILE THEY ARE FIGHTING ZOMBIES and doesn't tell the hero. Guess what she finds in the hallway? Apparently, she's never watched a horror movie in her life, either.
Oh, and let us not forget the 'sniff, sniff, you're my wolf-mate' trope. Can someone please, pretty please, put this trope out to pasture and shoot it? With a nuke? I get the idea of destined mates, one person in all the world is romantic, but the sniff test is lame. And it's lazy writing. And it totally disempowers the heroine. Mating for life is awesomely romantic but sniff, sniff we are going to bone for all eternity and you have no say whatsoever because it's destiny, pisses me off!!!!!
Stepping away from my rant box now. ;)
What saves this story (other than a terrifically dark universe) from being the flag bearer for trope nation is getting to know some the sequel bait and getting to know the world-building through their eyes.
Would I rec it? Yes, especially if you like the darker, creepy universe aspect, but be ready for mega tropes out of trope nation to rear their ugly, little, well-trodden heads in the worst moments.