The 100: Day 21 by Kass Morgan
I don't want to say too much about Day 21 seeing as it is a sequel and I don't want to spoil it for anyone, but I thoroughly enjoyed it. I often hear people saying that the show is way better and the books aren't worth the time. While the show is more action packed so far, the books are different and good in their own way. If you can separate the two in your mind, then you can enjoy them both. In Day 21 the 100 make some new discoveries that can change things for everyone. There are adventures, there are some mildly steamy scenes, and some serious eye opening. I hope more people decide to pick it up because, I feel it is worth the read. Have you read any of the books in this series?