Legend by Marie Lu

June and Day could not come from more different backgrounds.  June is a prodigy from a family of prestige and money.  Day is a notorious criminal who grew up in the slums.  They both live in the Republic controlled Western United States and would never have crossed paths if it weren't for the night when one of Day's break-ins went wrong and June's brother Metias got killed.

Now, Day has been accused of killing Metias and June is on the hunt for him.  When the two finally meet, their worlds start to change and they start to realize that nothing is exactly the way they thought.

This is another dystopic adventure featuring a plucky bright heroine.  One of the main differences is that June knows just how good she is and has faith in her abilities.  June can be a bit naive, and the ending of the book does kind of dissolve into some schmupitude, but aside from that I was really absorbed in the story.  Day is a hero who is too good to be true, but so likable that you don't really care.  I can't wait to read the next book in this trilogy (I think it's a trilogy) because I want to know what kind of change Day can really achieve.