While John Fowles uses elements of English history in the novel, it is a work of fiction. One term often applied to his approach in this novel is "postmodern." He uses some techniques found in both 19th- and 20th-century fiction, along with adding his own twist, resulting in a highly original creation.

The character of Charles draws on several real scientists of the era and earlier decades but is not meant to represent any one of them. His name references the early 19th-century James Smithson, known primarily as a chemist, for whom the Smithsonian Institution is named. Charles references Charles Darwin. Another evolutionist model was named Charles Lyell.

The character of Sarah is more ambiguous. She seems less like a real person and is often shown in terms of Charles's fantasy projections. Her models seem more literary, such as the heroine of Thomas Hardy's Tess of the D'urbervilles.