This is a crime novel. It has aspects of romance, but not very pronounced.
There is a mystery behind the novel, which is the identity of the original author. While reading it, I noticed that whoever wrote it, has a good knowledge of close combat, less of guns. Is probably male. He's not very good at writing romance though.
That was one problem I found with the novel. The romance is very forced. In the TV series, the romance comes about slowly, and seems like a natural progression of their relationship. Here it seems sudden, and almost like it's not a part of the whole narrative. The famed sex scene was okay, though I'm not a good measure of its quality nowadays.
The crime part was pretty good. A bit slow going at times, but the mystery was interesting, and while you don't realise the solution on the fifth page, it is solvable. The number of deaths is not ridiculously high as in the case with some crime stories. The depiction of the action is good, and understandable for the person not knowledgeable about combat and arms.
Overall, it's not a bad book. It's enjoyable for a quick read. Won't rock your world, or have you reaching for the next instalment right away, but fun. So I'm giving it 3 stars. If the romance was actually hot, I'd give 4.