Josiah Henson's autobiography is here. It is short enough and written in a simple enough style that it can be read in one sitting.

I feel a curious kind of affinity to Henson simply because at a tender age I read a biography of him, and then persuaded my parents to take us to the historical site, which wasn't terribly far from where we lived. My most vivid memory of that event was a bout of profound car sickness - I'll spare you the details, but my father did describe it as a "sterling silver performance" ...