Another book you could check out alongside the Rinzler one’s would be the Secret History of Star Wars by Michael Kaminski. It’s an unofficial book about the saga’s development, so while the book might not be written as professionally as Rinzler’s, you can be worried less about revisionism, as his main focus is how story ideas changed over the development of the saga. So you get Rinzler’s books and Kaminski’s and compare the two. It’ll probably give you a solid idea of the complete development of these films.