Reading the Narrative of the life of Frederick Douglas was a review for me here, since you're required to read it for US history with Dr.G. So, I really didn't factually learn anything about it. I did, however, get to look at the story and actually analyze it and read into it more (basically, look at it not just for facts to pass a test). The story was very descriptive, and allowed you to actually be there, rather then just tell you how it was. You're able to experience what happened. Since the story is a narrative, you know (atleast have a good idea) that what's happening was true. It's a first hand account of something, which can really play with your sences.
All in all, the book was pretty good.