I dig dystopia. The whole "big bad awful future" stuff is among my favorite thing to read right now, so, of course, I loved this book.
In Beatrice's world, there are four factions: Dauntless, for the brave, Amity, for the peaceful, Candor, for the honest, Erudite, the intelligent, and Abnegation, for the selfless. The society deems that you must live with your faction of birth until the age of 16. At that point, you get to decide your faction. Many choose to stay with their faction of birth ("faction before blood" is the motto, so you don't see much of your family if you go into a different one), but many also choose to change factions.
Beatrice loves her family, but she doesn't feel as selfless as the rest of them. While they truly personify the meaning of the word, she feels more selfish and like she doesn't fit in with her faction.
Before you get to choose your faction, you are put through some mental tests to determine where you might fit the best. The vast majority of people show a propensity for one faction very clearly. Beatrice, however, does not. She is a clear split in three equal directions. This is known as being Divergent and is terribly dangerous. Her test administrator tells her to keep this fact a secret because most people who are known Divergents end up dead.
On choosing day, Beatrice chooses to become Dauntless. They are put through brutal and rigorous training at the Dauntless compound, but Tris, as she's now known, is coming out on top. As they are nearing the end of their training, political upheaval begins and Tris, because she's a Divergent, is one of the only people who can save her blood family.
This book is simply amazing. The sequel, Insurgent, is coming out in May. I promise, you won't be able to put this one down!