Sarah, Plain and Tall is a simple story of a family that needs a mother and of the woman who gradually fills this need.

It is not a tale of wild action or frightful events. Instead, it emphasizes the humanity of characters who yearn to be loved but fear they may be unworthy of love. The novella focuses on honest emotion and portrays characters attempting to cope with complex feelings.

Sarah, Plain and Tall is popular with young readers, who enjoy its vivid recreation of a different era and appreciate MacLachlan's understanding of the universal emotional needs of young people.