I'm kind of unsure of how to rate this. I wasn't entirely engrossed in it but I did like it by the end. 3 star, I think.
At the beginning of this I can't say that I saw much of a blooming relationship between Mal and Alina. They'd been friends for years and though Alina liked him romantically, Mal didn't seem to feel the same way.`
That's probably why when the Darkling started to show interest in her that I jumped on ship with it and waited for something to happen. Only when something did, I wasn't entirely convinced by it.
As for the rest of the plot with the Unsea, I found myself getting more into it the closer we got to the end of the book as deception and intrigue came about.
I definitely think it has left me intrigued enough about the outcome of the events following the ending, that I will continue the series at some point.