Ok, I have to start by saying that I previously read the fic, so I had a few things to compare it to.
In general, the main plot is the same as the fic, however the book is a much cleaner version of it.
In terms of the suspense/mystery thing, it was good. Not too complicated and nothing jaw-dropping, but it was well done and entertaining. The book cleaned this topic from the fic version, so this was much better than that one.
However, I think two things could've been better in the book.
One was character development. Emilie suffered a lot during her life and she buried all that deep inside (understandably). Now we're adding a stalker and I have no idea how she's even standing. It was clear that she needed professional help, asap. It was suggested to her and she even agreed. However, nothing was done in that regard. No steps to real improvement, only talk of that. Also, I felt we were mostly told about her story instead of shown. She showed many times how difficult it was to her to even think about her past, yet after a few conversations she simply shared her entire story to people she barely knew. I just don't think that was believable.
Similar things could be said about Nathan. He felt guilty about his uncle dying for 14 years, yet after a few kisses with Emilie, he simply felt that it was time to let go and not only that, but he actually did let go of the past. It was simply too fast and rather anticlimactic.
The other thing that could've been better about this book was the romantic aspect: it simply wasn't there. For the first half of the book they behaved like SWAT dude and victim girl and that is okay (his job was at stake), but then at the next second they were kissing, having sex and saying 'I love you's. All of this happened in the second half of the book and I have no idea where it came from. Emilie and Nathan simply had no chemistry. I didn't care if they ended up together or not. Actually, it would've been more believable if they remained as friends in the end. Their 'getting together' was way too rushed and forced, there was no real flow from strangers to lovers. It wasn't natural.
In this subject, I personally think that the fic did a much better job at it. In the fic you could almost feel the attraction and the UST, you just wanted for the characters to end up together. Sadly, in the book the chemistry was heavily edited. My thoughts are that the book wanted to focus on the suspense part of things and not the romance. If that was the case, then it succeeded. The romance clearly took the second place.
So, if you're looking for a suspense, this might be the book for you. If you're also looking for romance... well, it wasn't the book for me.
I liked it, but didn't love it.