Two details particularly caught my eye. The first is that Douglass had a fascination with, of all people, Daniel O'Cornell, and drew direct parallels between the situation of American slaves and of the Irish. I guess the two causes shared the buzz-word of 'emancipation'. Looked at from 170 years on, now that O'Cornell (somewhat unfairly) is seen as a rather conservative revolutionary by Irish standards, it's an interesting juxtaposition.
The second point is Douglass' culture shock on moving to the free states of the North and discovering, to his amazement, that white people who did not themselves own slaves were not necessarily poor. He had expected Northern society to reflect the white working class lifestyle of Baltimore (where he had persuaded white kids to teach him to read by giving them the bread he got from his rich owner). It's an interesting perspective both on how little slaves were allowed to know about the outside world, and on how slavery impoverished the whole society.
It is interesting to contrast this with Fanny Kemble's account of life on a Georgian plantation, written at almost exactly the same time (though published 25 years later). The life of slaves in Georgia was certainly worse than in Maryland, which means that Kemble is more circumstantially dramatic, but of course Douglass' account has the merits of being that of a participant rather than am observer. Still, the same subjects come up relentlessly in both: white men using slave women to bear their children, whipping them to a pulp when they did not comply, and denying their slaves any change of education. Both are essential reads.