This review will contain spoilers!
In many sentences:
There were times when I really enjoyed the story that was being told in Finnikin of the Rock. Unfortunately, the lack of consistency among the world and characters that Marchetta created made this, ultimately, a negative reading experience.
First, let's discuss the inconsistency of the world. Marchetta was generous enough to provide the reader with detailed maps of the world she created. I did find myself referencing these maps frequently, and as a result I did develop a clear geographical picture of this world in my head. Surprisingly, this actually ended up being detrimental for my enjoyment of the book. At some points, the characters would be able to travel across the entire continent in a matter of a day or just a little more (such as when they leave the cloister, having just met Evanjalin for the first time). At other times, however, traversing a much smaller distance (such as the journey to the rock villages after leaving the boat) would take 4 or 5 days. This kind of inconsistency really frustrated me while reading it, and I couldn't help but notice it each time it happened.
The characters were also inconsistent in the sense that they didn't behave in believable ways. For example, just before Evanjalin turned Finnikin into the authorities, they had their first semi-romantic moment (page 69). This came out of nowhere, though, with no relationship development leading up to it. It was almost as though we were just expected to accept this because they were obviously going to have a relationship at some point, so why not start now? Their relationship became continuously more annoying as Finnikin or Evanjalin would get annoyed at the other, leave for a ridiculously short period of time, and then magically no longer be upset with each other. Finally, the whole idea that Finnikin would not want to be king so much that he would refuse to marry Evanjalin as utterly ridiculous. How could we believe he loved Evanjalin so much, but not enough to overcome his fear of being king? You can't have it both ways, either he was madly in love with Evanjalin, or he wasn't, and the kingship wouldn't even be an issue.
As I alluded to above, the story itself was a redeeming part of this novel. As much as the characters and the geography of the world suffered from inconsistencies, the story did not. There was a clear plot, that moved along nicely. There was one big problem for me, though, and that was the idea that it took 10 years for people to find Trevanion and the others. This world is extremely small, and the book moves so quickly from place to place that it feels like there are only about 10 places these people could be hiding. So why was this not all done years before? It wasn't difficult for them to find everyone they wanted, once they started trying, so it's hard to believe it would take so long for these events to transpire.
The most redeeming quality of this book was, surprisingly, the thief Froi. He is the only character to show consistent, believable growth, and to develop in a natural, meaningful way. His decision to follow Evanjalin after her lie about Balthazar was actually meaningful. Similarly, his insight into how he needed to get to know about and care for the land of Lumatere before he could be asked to protect it was probably my favorite moment because it was the most intellectually satisfying as a reader. You actually felt like you were beginning to understand how this exiled thief who knew nothing for his homeland was growing and maturing. It was actually quite great.
Ultimately, there are just too many flaws in Finnikin to let me recommend it. I wouldn't be opposed to giving another novel by Marchetta a chance, because she definitely shows promise, but this one should be a pass for most readers.