Liked the movie? Read the book!
If you liked the movie, you'll LOVE the book!
Deceptions (by Judith Michael) is an incredible book and it varies enough from the movie that you'll be surprised. They took the movie in a completely different direction.
About 10-15 years later, the writers (Judith Michael is a husband/wife writing team, who by the way, inserted themselves as characters in the book, as friends of Sabrina) released A Tangled Web, which continues the story of the ill-fated twins.