Look at and think about the images under these links: The Anti-Slavery Record; The Slave's Friend; Picture of Slavery; and the "Amalgamation Series"
From An Appeal: Preface, Chapters 5 and 8
If you want, compare what Stowe says in these chapters about (and what she quotes from) the slave narratives of Lewis Clarke, Frederick Douglass, and Josiah Henson with the originals by using these links (the UTC site's SEARCH ENGINE can help you locate passages Stowe cites).
Theodore Weld's 1839 book, though not a "best seller," was probably the best known abolitonist representation of slavery before Uncle Tom's Cabin appeared. And as Stowe reveals in the Key, she consulted it while writing the novel. If you want to take a look at it for yourself, feel free to use the link here to do so.
If you want to see more on Anti-Slavery, help yourself.