Child Called "It"

I am still reading this book by Dave Pelzer which is his story of being abused growing up by his mother. It is the most horrifying thing I have EVER read. She made him eat shit, drink ammonia, denied him food regularly and she stabbed him. And his father stood by and did nothing. And she didn't do anything to his siblings.
I had no idea that anyone had the capacity for cruelty to abuse a child so severely.