The book The Forty Rules of Love contains two stories told in parallel: firstly, the story of Ella and Aziz in the 21st century; secondly, the story of Rumi and Shams in the 13th century as told by Aziz in his novel Sweet Blasphemy which Ella is reading and reviewing. I would say that the main point of Şafak's book, what sets it apart from many other modern romance novels, is the story of Rumi and Shams: it teaches the average modern reader a lot about life in the 13th-century Middle East, and it also adds context to the Ella-Aziz relationship by comparison. Why, then, didn't Şafak simply write the book Aziz did - a story about Rumi and Shams, without giving it any 21st-century context?
Why is the frame story included in The Forty Rules of Love, rather than just making it a gripping and entertaining historical tale about Rumi and Shams?