This is a genuinely original, imaginative and ambitious novel which Donoghue pulls off brilliantly. Written through the voice and perspective of 5 year old Jack, we witness his happy and secure solitary life with his mother in Room. Playing on the tradition of other naive child-narrators (e.g. Pip in Great Expectations, Maisie in What Maisie Knew) we experience his exuberant take on what he naturally assumes is normal, only the sinister implications of their life seep through the edges to unsettle us as readers, revealing a far more menacing reality that he doesn't see.
This isn't a plot driven novel full of twists and turns, instead it is an intelligent and detailed exploration of the way the human mind constructs its own reality. Full of tenderness as well as pain, this celebrates the relationship created by this young mother with her son, and reveals the enormous potential for resilience in the human spirit.
The second half of the book where Jack experiences Outside for the first time is fresh and imaginative, sometimes funny but also agonising as this solemn 5 year old understands for the first time that the world doesn't consist of just him and his mother, and that the rules which they lived by can, and should, be broken.
There are a few small points where Donoghue stumbles (the first TV interview felt very false and forced; some of Jack's naivety towards the end takes on the tinge of adult satire and I felt like it was the author, not the character, talking about how people have too little time to enjoy their lives).
But these are small niggles in a powerful and overwhelmingly confident narrative. I started this in the afternoon and was literally unable to put the book down till I finished it that night and even after that Jack's voice still haunted me. It's quite rare for me to be really gripped by a contemporary literary novel but this one managed it effortlessly: highly recommended.