This book takes of right were Divergent left off. A battle of factions in this dystopian society leaves characters deciding on how to choose sides and what to do now.
There's not much of a recap, so if it's been awhile since you read the first book, it might seem a bit confusing at first. In this second book of Roth's trilogy we learn more about the Divergent (people with the traits of multiple factions) and about the Factionless - those who belong to no faction. They move from the background into prime-player status. (Roth also focuses a bit more on the Candor and Amity factions.)
This book is darker than Divergent. Tris deals with guilt, grief and betrayal while sorting out what needs to be done. There's a secret. Should it be kept or revealed? There's a nice cliffhanger at the end. Good, face-paced read.