Thimble Summer features clear, unadorned prose. With descriptive power Enright creates moods and images that reflect Garnet's feelings, as in this passage that depicts Garnet's twinges of fear as she and Jay walk along the wooded riverbank at night: All along the wooded banks owls hooted with a velvety, lost sound; and there was one that screamed, from time to time, in a high, terrifying voice. Garnet knew that they were only owls, but still, in the hot darkness with no light but the solemn winking of the fireflies, she felt that they might be anything.

Although Garnet's growth and personality are the primary unifying factors of the novel, symbols also help pull together the episodes. One significant but simply presented symbol is the silver thimble Garnet finds beside the river: " 'it's solid silver!' she shouted triumphantly, 'and I think it must be magic too...