Edgar Hilsenrath
Nacht
Ranek, a teen struggeling in an Ukrainian Ghetto to survive. I was 15, the same age as Ranek, when I read it. But this is no YA book, it was written for grown ups.
The horrors are even worse as the author is never whining or trying to make you pity Ranek. It is literature of the highest sort and utterly disturbing.
I did not stop reading it, but I will never be brave enough to re-read it.