In truth it is "unputdownable" and you might read it in one go, reluctantly putting it down to eat or go to work etc. What makes it so is the 'strength of the weak' - the sheer will to survive of a child who was being treated so badly.
The only thing I can compare it with is the Russian writer Solzhenitsyn who writes about the prison camps. You would expect that to be pretty bloody grim - yet "A Day in the life of Ivan Denisovitch" is about the triumph of the human spirit - Solzhenitsin would say the soul - over awful conditions. It makes compelling reading.
As a reader I felt as the child felt, it is really powerful writing. When he was bad he was punished by missing meals. Then he was a "bad boy" because he stole food, so he was punished by not being fed and the punishments escalated. Some of the punishments (and I do not doubt the story) seem beyond belief.
Extraordinarily, he believes his teachers "risked their jobs" by arranging for the police to investigate and take him away from his abusive mother. There must be some differences between American and British custom and practice in child abuse cases. The immediate involvement of the police rather than social services would be one difference but the idea that teachers feel their job is on the line if they take action is a considerable difference. This also reflects the time of the story, the author is now an adult.