This isn't quite a novel. I feel for the author, because his ambition to write a novel is apparent on each page, and even embodied by the principal character. It is a common desire, and it becomes poignant when the author is aware of it, and aware of his shortcomings, and can't quite solve them.
In this case Thubron has the adventure story, the elements of an interesting interaction between characters, and the possibility of a developed moral and ethical theme. But he just can't build characters, can't give them life, can't break out of the feeling that each scene is imagined as it might appear in a movie. We see that, and so does he, and we root for the author, but it just does not add up to a novel. A screenplay, yes, but not a novel.