Are you trying to write a thesis that in some way compares these two books? If so, I would focus on their differences. In Black Like Me, a WHITE MAN pretends to be a black man and travels through the south in attempt to experience what prejudice is like. He takes drugs to change the color of his skin. It is a non-fiction book. In I Know Why the Caged Bird Sings, Maya Angelou, a black woman, tells her life story, how she actually DID experience not only prejudice, but many other traumas because of that prejudice.
Do you think it is possible for someone pretending to be black to really experience the depth of prejudice? Griffin, the author, determined from the get-go that he would not lie to people about what he was doing, so it was obvious, although well-intended, that he was not really experiencing TRUE prejudice.
Perhaps you could write about the depth of both experiences - compare what Griffin experienced to what Angelou experienced - "pretend" prejudice vs "real prejudice". There are lots of approaches you could take. You could focus on the "depth of prejudice experienced by Griffin vs the depth of prejudice experienced by Angelou." You could also focus on the perspective of blacks - do some research - how did blacks react to Griffin's experiment vs how they reacted to Angelou's real experiences. The depth of emotion in the Angelou work is far more profound than the Griffin work, mostly because Angelou's work reads as a novel, even though most of it is true, whereas Griffin's is more journalistic in its approach. Does the writing style affect the effectiveness?
I have thrown out some ideas that I hope will help you. Good luck.