I think this could have really been amazing. The shifter element wasn't the most focused on, but it was brought up in the beginning so it wasn't totally overlooked. The book was more about Jack than anything else, I think. And maybe the relationships, but it definitely felt like Jack's book to me at times.
I really loved Jack and I liked Marius. They were strong characters and I enjoyed different things about them. Jack was definitely my favorite character in the story, though. He was just so sweet and yeah, he was struggling after his ordeal. And I thought his reactions were pretty much realistic. As for Marius, I liked his protectiveness in some scenes and I think he seemed like a really nice guy. But I didn't buy into him as much as I did Jack.
I think this book kinda fell flat for me when they started something. For me, there was more chemistry there before they got together. It just felt forced at times and I enjoyed the moments with Missy more than Jack and Marius as a couple... Not something you want to say about a book. But it wasn't a bad book, just not something I overly enjoyed.
So while I didn't fall in love with this book, I can see people enjoying it. And if you want a shifter story where the focus isn't solely on the shifter thing, then maybe you should give this one a go.