Note: This is not the book's cover
Following the theme of dystopian trilogies, Insurgent plays the role a second novel usually does: development of the characters and the push of revolution that the first novel established as needed. In the Hunger Games trilogy, we see the second novel, Catching Fire, as the way in which rebels push their revolution into action. Insurgent spends the entire story on the revolution that began at the end of Divergent. Of course, with a third book in the series, it doesn't end with all the loose ends tied up. There's still the idea of "what now?" So, the revolution is far from over.
It is hard to discuss a book where most actions are important pieces to the story without spoiling something somewhere. But assuming you've read Divergent, I can say that Insurgent calls into question the relationships of which Divergent made the reader seem so sure. Uncertainty reigns in whom a person can trust and the mystery of some important information that only a few know and yet seems worth killing half the community over.
Insurgent is a whirlwind of uncertainty that ends with a shocking revelation about the existence of the five faction society and the purpose for which none of them realize they are to live.
Are you a fan of dystopian lit or does it all sound the same to you?