Complex sentence: The book based on the film gives Boo's "real" name as Mary Gibbs, the name of her voice actress who also happens to be the daughter of Rob Gibbs who worked as a story artist on the film.
Split into simpler sentences: The book based on the film gives Boo's "real" name as Mary Gibbs, the name of her voice actress. Gibbs also happens to be the daughter of Rob Gibbs who worked as a story artist on the film.