Although Uncle Tom’s Cabin by itself did not start the Civil War, it did increase tensions between the North and South by bringing to light the inherent cruelty of slavery.
Prior to its publication, very few people in the North really understood slavery outside of the abolitionist camp. Most northerners understood its significance and may have seen a slave or two at some point, but most parts of the north were far removed from the realities. Hear about the whippings, auctions and the violence did very little to move most northerners to action.
When Harriet Beecher Stowe published her novel in 1852, it was a runaway success. People in the north read it cover to cover and were stirred to action. In some parts of the north it was sold out for months. Many northern newspapers published excerpts from it while people waited for more copies to be printed. In the book’s climactic scene, the slave master character Simon LeGree beats Uncle Tom to death. This image stuck with northerns, and soon they began to associate southerners with the character of Simon LeGree, seeing all slave owners as cruel, barbaric monsters. Many joined abolitionist societies and began crusading to end slavery.
The book increased distrust and tension between the two sides, but it didn’t cause the war by itself. You could say that no other book was more responsible, but many other actions contributed to the Civil War. On a side note, when Abraham Lincoln finally met Harriet Beecher Stowe after the book was published, he did remark, “So you’re the little lady that caused this great war?” Perhaps it deserves a lot more of the credit than many historians give it.