Pandemonium by Lauren Oliver
Delirium was really amazing, though it almost read like a contemporary even if it was set in the future. Not much adventure happened. It's the complete opposite in Pandemonium. Lena goes on a lot of adventures and she's really learned how to survive. She definitely developed greatly as a character. Plus, Pandemonium is written in both then and now, so you can see what happened in the past as well as what's currently happening with Lena.
The Evolution of Mara Dyer by Michelle HodkinThe Unbecoming of Mara Dyer was a bit crazy, though The Evolution of Mara Dyer was even crazier. So much happens and Noah and Mara get messed with and Mara learns even more about herself... it's just outstanding. I don't want to give away anything, so I say just read it!
A Million Suns by Beth Revis
Across the Universe had quite a mystery. I thought there wasn't going to be anymore. I was wrong. A Million Suns brings a completely new story to the table. We even learn a lot more about Orion, which was really cool. I really hated him until I read this book.
The Prey by Andrew FukudaI thought The Hunt was super amazing, but The Prey is something really different. The gang travels to another place where things are even crazier than they seem. Plus, some new love interests arise while others bloom. I'm definitely excited to see what happens because The Prey left me wanting more!
What sequels did you like even better than the first book?