(Minor spoilers ahead.)
The first half of the novel meets the dual challenges: sustaining interest in a small child's narration, and in dramatizing the details of room (in the acknowledgments the author thanks her brother-in-law for his "unnervingly insightful advice on the practicalities of Room.") The middle passage of the book is both frightening and affecting. I was really rooting for the details of police work. It assuaged some of the frustration I accumulated while watching The Wire.
The point, I think, is that people want to revert to their conditions of comfort and control, even when those conditions are horrifying and the control isn't theirs. (Or as a pretentious TV pundit puts it: "The inner child, trapped in our personal Room one oh one.") Both Jack and his mother flail when separated, but his mother has it particularly hard; she has to take control, whereas he only has to receive it. "You know who you belong to, Jack?...Yourself," the child is asked. His unspoken response: "He's wrong, actually. I belong to Ma."