I loved this. I'm so glad that I decided to read it. Even though it is a prequel, you definitely need to read the first 3 books before you read this one (it contains spoilers). This series was so good and kept me on my toes the entire time. I feel like people who read this and didn't like it were those that assumed that this was a prequel that involved Theresa and Thomas and the other Gladers, but that's not the case. This prequel actually explores the beginning of the sun flares as well as the virus known as the Flare.