I think I've read the book on which the movie was based, but in my edition of Dumas' works it's called Marguerite de Valois. If La Reine Margot dealt with the St. Bartholomew's Day Massacre, then it's the same book, and yes, it's definitely worth reading. (I saw the movie a long time ago. I remember that I enjoyed it, but I don't remember much else about it, such as plot or who was in it. Bad fan!)