Insurgent

Insurgent is a fantastic (if not slightly infuriating—but in a good way) sequel. One of my favorite aspects about the Divergent trilogy is the characters—they're complicated and layered, make (plenty) of mistakes and have their own flaws and struggles to deal with. As a bonus, Roth doesn't rely on the traditional love triangle seen so often in YA novels—instead, she chooses to explore the complexities and difficulties of a relationship, which turned out to be very effective (and also often the source of the aforementioned frustration).

For those of you who have read Divergent and haven't yet picked up the sequel, I highly recommend it, and for anyone else who enjoys well-written dystopian YA books, I can't recommend this trilogy enough.