It's been three years since I've read Divergent (three years? Really?), so what do I remember about this storyline? Admittedly, not enough to remember what's going on in the start of Insurgent, besides Something Big is happening that Tris has something to do with. 
 Unfortunately, this book suffers greatly from Middle Book Syndrome: The action was set up in book one, and the resolution will happen later, but in the meantime we... wait. We hop from faction to faction, learning who's a comrade and who's a traitor, trying to track down the Truth. And of course, we're left with this really awesome cliffhanger that means I have to go buy book #3 tomorrow. 
 But despite my indifferent toward the plot, I really like Tris as a character. She's tough enough to do this all on her own, and no one is directing her toward/away anything because "she's a girl." These characters are not identified by gender; they've latched onto their factions instead, which is a strange and creepy kind of identity. And here, more and more of the Divergent are revealed--those exhibiting characteristics of multiple factions--and everyone feels a little more uncomfortable about it. 
 Discomfort is good. Identifying with your faction is good. Because this is all going to break down soon, and it'll be glorious chaos.