"The Moon and the Sun" (1997) is an excellent fantasy novel by US science fiction author Vonda McIntyre. The novel is not a standard fantasy, but rather an alternate history novel with fantasy elements. It won a number of awards, including the 1997 Nebula Award for Best Novel (beating the favorite "A Game of Thrones" by George R. R. Martin).

The story is set in 17th century France, during the reign of the Sun King Louis XIV, at his court in Versailles. The novel is filled with a large cast of courtiers, many of them historical figures, who are all competing for the favor of the King. The main character, Marie-Josephe de la Croix, assists her brother, Father Yves de la Croix, in the scientific study of a recently captured sea monster. The King hopes to gain immortality by consuming part of the creature, but as the study continues, Marie-Josephe discovers the sea monster may be more than a dumb beast. This discovery tests Marie-Josephe's loyalty to her brother, her king and her religion.

Vonda McIntyre thoroughly researched the historical setting for "The Moon and the Sun" and created a very convincing setting, filling it with believable and well-rounded characters. Because of the level of detail, the novel can be enjoyed as a historical novel and a fantasy. Very highly recommended.

Note: the novel originated as a short story, written in the form of a fictional encyclopedia article, "The Natural History and Extinction of the People of the Sea", which was illustrated by (fellow author) Ursula K. Le Guin and indirectly inspired by research done by the late Avram Davidson, another brilliant SF writer. The novel also exists as a screenplay.