First of all, if you hate cliffhangers, avoid this book or just buy The Scorch Trials before finishing it, otherwise you'll go insane.
Stepping to the story... It begins with our main character, Thomas, arriving to the Glade with no previous memories of his life. There he meets the other teenage boys living in the Glade and gets to know that they've been searching for a way to escape from the place (that's surrounded by a maze filled with creatures, known as Grievers) for two years. Thomas will learn to live in the community as he finds out as much as he's able about the Glade and the Gladers. Things will change abysmally after a girl named Teresa arrives and triggers "the Ending".
I personally liked the story a lot, because it compells you to keep reading and I didn't want to stop! I had so many questions without answers, as Thomas, and I managed to solve them along with him just to get a dozen more of questions. And then the ending came and I was all "WTF, no, I NEED THE NEXT BOOK"
Writing is just okay, nothing impressive. But it's fine.
Characters... Mhm... So and so. I don't love any of them, I don't hate any of them either. Thomas, Teresa, Alby, Newt, Chuck, Minho and Gally are the ones that we get to know the best, even when we know almost nothing about them because, hey, they don't know a thing about their past!
In a sum up... It was a good story. I liked it, I liked the concept and the idea. It could have been better, yeah, but I wasn't disappointed with it. So, moving right into the next book, yay!