The Amish interpret the whole Bible, Old and New Testaments literally. Their interpretation is in part subject to traditional dogmas such as belief in the Trinity, which is not accepted by all fundamentalist groups, e.g. Jehovah's Witnesses. Their culture and their faith are inextricably entwined.
A very good book about the Amish, which covers their religious beliefs as well as explaining their culture, is "Amish Society", by John A. Hostetler.
The late Mr. Hostetler was born into an Amish family, but left the Amish, becoming one of the world's leading authority on the subject.