This is the first of a series that accompanies another series, as a prequel, and although the author says it's fine to read in chronological order, I suspect I would have enjoyed it better if I'd read the other series first.
As it is, it was heading into a solid 4, until the last quarter, which felt rushed. One of the main characters is not introduced until at least half way through the book, and I found that didn't give me enough time to understand him or his motives.
And the MacGuffin that is at the center of the second half just seemed needlessly mysterious - I found myself disliking the character that set it up, and the emotional manipulation he used to do so.
As seems to be common lately, there were two completely separate narrative threads that didn't meet for the majority of the story, and while I see a lot of other reviewers didn't much care for one of them (Gwen's story) I rather liked it, particularly in the first half.
All said, it's a good high-fantasy hack and slash fest, and I did enjoy it, for most of the book more than my 3 star rating implies. And I will certainly be reading the rest of both series.