I really did not enjoy the first book in the series (The Thief) but pressed on to read The Queen of Attolia based on the recommendations and reviews of some people whose opinions I really respect.
Well, I'm very, very glad that I did.
This book hit everything that I was hoping for in the first book. For one, the writing was better (not that the first book was poorly written, but the change from first-person POV in The Thief to third-person POV in The Queen of Attolia really improved the story). Secondly, Gen became a much more likable protagonist in this book, in my opinion. I wasn't overfond of him in The Thief, but he really grew on me in this installment. Furthermore, the plot was just more interesting for me in this book than in The Thief. The Thief seemed to stretch out too long over trying to steal a stone, whereas The Queen of Attolia has a lot more going on - politics, intrigue, war, lore, romance, and all sorts of goodies.
Anyway, sorry to turn this into a "Book 1 vs Book 2" rant rather than a review, but there are tons of wonderful reviews already on here that will tell you what you need to know (since what you need to know is that you should read this book).