In short, the plot was interesting, but the characters were bland.
The Plot: There's not much I can say about the plot without using spoiler tags since there are practically no developments until the last few chapters of the book. So many details are hidden to the reader that it's almost annoying at some points. Nevertheless, I'm interested in finding the answers to Thomas' unanswered questions and I plan to read the next book in the series.
Here's what I can say about the plot without giving anything away:
Thomas wakes up one day in a dark box with most of his memories completely gone. He finds himself welcomed to a place called The Glade where a group of other teenage boys have made themselves at home. The Glade is surrounded by massive stone walls that open up to the surrounding maze during the day. All of the other boys also had their memories wiped, so no one knows how they got there or how to escape. Every day, they run through the maze trying to find signs of an exit. And every day for the past two years, they've found nothing. Thomas has a weird feeling about The Glade, though. It seems familiar to him somehow. Not surprisingly, things start to change soon after he arrives. Things get pretty gruesome, too, so be prepared for some violent scenes.
The characters: The majority of the characters are grossly underdeveloped. You couldn't take the characters out of this story and place them in another and know exactly how they would act. I was disappointed because the author spends a lot of time telling us how everyone is feeling instead of showing us. There are also a lot of lines like "Even though Thomas couldn't remember his past, he knew this was the saddest he'd ever felt." Descriptions like that didn't add much to the book. Hopefully there is more character development in the second book.
The narrator: I think the narrator had a great variety of voices for the characters, but his regular narrating voice did not fit the story. It was the type of voice I would expect to hear for a nonfiction book, not a young adult novel.