I think this book suffers more from being a tie-in novel for the 13th Age RPG than anything else. Even for an RPG setting, it's deliberately left as more of a blank slate for a Games Master to fill in.
Unfortunately, Stolze, perhaps because he wanted to keep the story accessible for any Games Master to fit in their world, didn't fill in enough of the blanks for me. The world really felt very undefined and vague and I never got a strong sense of place, which I think is important when your setting is a fantasy world - especially one so fantastic as the Dragon Empire.
There were also a few stylistic quirks I found a bit distracting. There was a tendency to start in medias res at the beginning of chapters or scenes, which was a bit disorienting and quickly became tiresome (a couple of times the characters also started out anonymous, and I guess we were supposed to pat ourselves on the back for working out who they were). Also, one character, whilst interesting, was badly let down by an unnecessary spelling out of their back-story to the main character, when some ambiguity would have been better.
The action was really well written though, and very easy to follow and some of the ideas and characters were very clever. For such a short novel though, the cast was probably a bit too large and none of the militia characters managed to make much impression on me.
A really big part of the 13th Age setting are the Icons and I was a bit disappointed that they didn't appear to be particularly large drivers of the action until the final chapter. Only one was really integral to the story up until that point, and that was through the magnificent-bastard Grossthorn.
If you're at all interested in the 13th Age setting this is well worth a read, if only to mine for ideas, but otherwise, I'd give it a miss.