Film: Snow White and the Seven Dwarves (1937)
Book: Snow White by the Brothers Grimm (1812)
First off, in the Grimms' version, Snow White is seven, which jars the modern mind a little when she gets married at the end. That said, this was one of Disney's more faithful re-imaginings of an old folk tale: an evil queen-slash-stepmother with a magic mirror; a band of dwarves; a huntsman; a poison apple; a glass coffin; a dashing prince.
The Disney version, however, omitted a handful of the gorier details, by far the most grisly of which comes at the end when the prince punishes the Queen for attempted murder by forcing her to dance at their wedding in a pair of red-hot iron slippers until she drops dead.
While the Grimms probably took their inspiration from a number of sources, the most likely is thought to have been Margarete von Waldeck, an exquisitely beautiful young noblewoman who lived in the Belgian town of Waldeck in the 16th century (in her town, children, known as 'dwarfs', worked in the local mines and lived together in large groups in single rooms). She is said to have fallen out with her stepmother and moved to Brussels in 1549, where she turned the heads of several noblemen, including Phillip II of Spain. But there was no happy ending for Margarete: just as the king-in-waiting planned to marry the 21-year-old beauty, she was mysteriously poisoned and died.