I've read this in a day, so I suppose "gripping" is a good word for The Wonder. I can see where this will be a story I'll forever remember, for it's told to a different tune than your average novel. 
 Firstly, I was enchanted by the characters. We never know whose side we should really be on until the very end. And I would even gamble to say that some readers may have a different favorite from me. I believed all of their backgrounds, their personalities, their motives and convictions... I trust these characters to be exactly as they are described, and I love and hate them equally for who they are. I believe you can really judge a book by its characters, and in this case, these characters are real and flawed and honest. 
 For a book so heavily based on religion, The Wonder never came across as pompous (to one extreme) or mocking (to the other extreme). To tackle a topic such as this, which typically weighs heavily for people, without offending either side is something to be admired. I've found that many people get the subject of religion wrong. There's no other way to put it other than wrong. But not here. Emma Donoghue has managed to weave this part of humanity into her story with great tact. And at the same time, she's given readers on all points of the spectrum something to consider and think about long after turning the final page. 
 I also loved the twists and directions this story took. I never really knew what to expect until the facts were revealed. I loved not being able to guess because all possibilities existed with equal merit. And the end brought me peace; I feel satisfied knowing the outcome. 
 I was first introduced to Emma Donoghue with her best-seller Room, which I really enjoyed when I read it a few years ago. I believe it's safe to say that Donoghue has turned out another good one with The Wonder. I definitely recommend.