The acting, from the boy in particular, was very good. I'm not sure which part I found most depressing - the most disturbing part was when he opened the cellar in the big house.
[SPOILERS AHEAD!]
I haven't read the book, and I'm not sure if we were "supposed" to think this or not, but I actually found the relationship between the father and son increasingly distressing. The father, wanting to protect the boy, saw everything and everyone as a threat, but the boy's instinct was to be more trusting - and most of the time, it seemed he was right.
By the end of the film, it was getting to the point where I didn't actually like the father any more.... it felt like it was
time for them to be separated, and the boy was actually
better off with the family he met. So I didn't see the father's death as the tragedy it was meant(?) to be...
I guess I should read the book.