Complex sentence: It was not widely known who had created the movie, rumors went around that behind the film was Andy Warhol, until 1999, when a book Taschen researched and written by Bruce Benderson was published about Bidgood's body of photographic and filmic work.
Split into simpler sentences: It was not widely known who had created the movie, rumors went around that behind the film was Andy Warhol. In 1999, a book Taschen researched and written by Benderson was published about Bidgood's body of photographic and filmic work.