What does Frederick Douglass learn about history of slavery through the books that he reads that lead him to detest his master, even though in some ways, as a boy, Douglass felt was "much better off" than some of the white boys in his neighborhood?

Douglass was born and raised as a slave, so he didn't know any different/better lifestyle. Most slaves at that time were illiterate but Douglass knew how to read and write and started reading whatever he could find in front of him: books, poems, political phamplets, etc. Once he was able to read History books he finally realized how slavery was cruel and unfair. That's when he wote: "The more I read, the more I was led to abhor and detest my enslavers. I could regard them in no other light than a band of successful robbers, who had left their homes, and gone to Africa, and stolen us from our homes, and in a strange land reduced us to slavery."