This is a good book. It was interesting reading about the inner workings and history of a family, albeit from the perspective of one person. As I was reading it I was seeing everything clicking into place and I was waiting for Sam to catch up. This didn't spoil things for me as it was a source of suspense in the story.
I remember driving across the Nullabor on a family holiday when I was a kid and I remember how fraught it could be. Hours of straight driving can send a child (and adults) a bit stir crazy, and I could feel that mounting impatience, boredom and fear in the kids, along with the revealing of Dettie's true state of mind.
While the story was written from the perspective of a child, the voice wasn't particularly child-like in some respects and showed a lot of mature insight. Sam not being able to speak probably resulted in him turning inwards, so this could be explained in this way. But there were a few times that I thought his line of reasoning and his emotional insight would have been out of reach for most kids. But none of this was bad enough to spoil my enjoyment of the story.
While the impending events were telegraphed, I kept reading because I wanted to see how they would get there; that was enough for me to happily keep reading. I also thought it was very clever that not all story lines were wrapped up. A particularly crucial one was left for the reader to ponder, and it was this that made me ask questions regarding issues around personal responsibility in the context of mental illness. And I will happily recommend any novel that gets me thinking.