The American Colonies during the days of the Revolution are the setting for [Two Valleys]….

Mr. Fast is unusually successful in conveying the mood and impression he depicts. He possesses also the knack of creating lifelike characters; his leading figures in their outlines have reality and act on their own volition, and the minor figures emerge as distinct individualities. The settled Pennsylvania village, with its Quaker meeting house and Lutheran church, is effectively contrasted with the wilderness beyond. The reader understands the spell of the wilderness…. Perhaps most characteristic of the mood of the earlier frontier America was the feeling of a future full of limitless possibilities. It is this element which Mr. Fast most vividly portrays.

"Frontier America," in The New York Times Book Review (© 1933 by The New York Times Company; reprinted by permission), October 13, 1933, p. 9.