"To the surprise of no one, I definitely thought Lila and Rebecca were going to kiss."

Divergent the Series, a Summary:
Divergent: Training montages, and the a shit ton of people randomly die for no reason.
Insurgent: A shit ton of people randomly die for no reason.
Allegiant: A shit ton of people randomly die for no reason: now with misogyny!

"People would die, and I just wouldn't care." A summary of the entire series/

*spoilers*
Yes. It's genetic engineering. You find out in book three. It's badly explained.