As an avid consumer of novel adaptations of fairy tales and having read Jessica Day George's previous two Princess books, I was looking forward to this. Though I feel awkward criticizing her work since I've heard Day George as a guest on the popular podcast Writing Excuses (Google it!), I have to say I was very disappointed by this novel. A few specific problems:
Pacing: A detailed, minute-by-minute account would be followed by a sudden jump to several days later, during which, apparently, characters undertook an entire journey across the country. Don't get me wrong: I don't need redundant detail of every mile covered a la George RR Martin, but a paragraph or two about the weather on the trip, a horse going lame, and a gruff innkeeper would at least make it feel like distance was covered and time passed. Furthermore, if this country is small enough that the characters can get from the border to the capitol city in a DAY, how is it possible that notorious bandits have successfully remained hidden in the forest for a decade? The attempted explanations of this are flimsy.
Exposition: Character provides backstory (usually from the first two books), then someone approaches him to provide additional context (in a very straightforward, dull manner), then he recounts the full story in pretty much the exact same terms to someone else, who then relates the story to yet another person. The reader has to sit through every explanation that one character gives to another, even though we already know it, just to confirm that the information has been passed. Can I get a little less talk and a lot more action?
Dialogue: Ouch. What happened? "Princess of Glass" had much better banter, probably because Poppy was a more compelling princess than Petunia. In fact, I think Day George was pining for Poppy a bit in the writing of this story, because Petunia comments several times in her inner monologue that her behavior "is more like something Poppy would do." Seems like Petunia's personality wasn't very well defined, so she came out more as a watered-down Poppy than as a unique character with her own story to tell.
On top of all this, I was finding glaring editing mistakes just pages into the book (mostly POV errors), so the whole venture feels rushed to me. I wouldn't say to avoid the book, but lowering expectations a bit is probably a good idea if you've read the first two.