In some ways, Uncle Tom's Cabin was a reflection of a certain point of view at a certain time. Its author, Harriet Beecher Stowe, was an abolitionist, and she, like many other anti-slavery activists in the North, was angry at the Fugitive Slave Act of 1850, which, among other things, required Northerners to return escaped slaves. The act turned many Northerners who had not thought much about slavery against the institution, because they thought Southerners, despite all their talk of states rights, were forcing them to support slavery.
In this atmosphere, Uncle Tom's Cabin was an incendiary book. It portrayed slavery as brutal and dehumanizing, and it vividly, sometimes with a great deal of melodrama, portrayed the ordeal that many escapees endured to gain their freedom. Chapter Nine of the book specifically highlights the injustice of the Fugitive Slave law, as it portrays Senator Bird, having voted for the act in order to preserve national unity, ultimately choosing to violate it to help Eliza and Harry escape. Upon finding out that he voted for the law, his wife chastises him:
You ought to be ashamed, John!…It's a shameful, wicked, abominable law, and I'll break it, for one, the first time I get a chance; and I hope I shall have a chance, I do!
The book, then, is not just intended to expose the horrors of slavery, it is intended as a call to action and an appeal to morality. While the book is often melodramatic, maudlin, and patronizing to blacks (many scholars and writers, including James Baldwin, have been very critical of its treatment of African-Americans) it also did much to drum up support for the abolitionist, or at least the Free Soil cause. Abraham Lincoln once referred to Stowe as the lady who started the "big war," and it was the book's effect on popular opinion about slavery that he had in mind.