Originally "White Palace" was to have been "White Castle", and in the novel specific reference is made to a real White Castle location at the intersection of S. Grand Blvd. and Gravois Ave. in south St. Louis, Mo., but the White Castle chain wouldn't give permission for their trademarked name to be used in either the novel or the movie, or allow the use of any of their restaurants for film locations. The diner used for the film's "White Palace" restaurant tried to change its name to White Palace after the film was released, but the studio refused permission, so it was renamed "White Knight" by its owners instead. It still exists and is open for business.
The trivia item below may give away important plot points.
Months after principal photography wrapped on the film, stars Susan Sarandon and James Spader were called back to re-shoot the ending. The original ending for the film followed the ending in the book where Max proposes to Nora in a restaurant bathroom and it's left up to the reader to determine whether or not she agrees. This ending didn't test well as audiences wanted a more definitive conclusion.