I purchased this novel almost entirely on the strength of it winning the 1997 Nebula Award. Now I find myself asking: "How on Earth was it even nominated, let alone win?" The Moon and the Sun is not a science fiction novel. True, it is a fantasy novel, but ultimately it's more an historical romance. Moreover, it's set in a period I don't really care much for - 17th century France.
That said, it is not a bad novel by any means. The period has clearly been very well researched, and many of the historical characters are very convincing. The heroine of the story, however, does seem a little over the top. She apparently is a gifted composer, artist, mathematican/scientist and horseperson (have you ever tried riding side saddle at a gallop) all rolled into one. Oh, and of course, she was a stunning beauty too.
Overall, The Moon and the Sun is quite a good read, and will appeal to those who like historical fantasy with a strong emphasis on romance, and where everyone lives happily after.