Writing a book about Joan Didion is a good way to discover that many people love her but far fewer people have read much of her work. In the five years since I started working on my book We Tell Ourselves Stories, I’ve surprised a lot of her admirers with things they didn’t expect: her conservative leanings, her John Wayne adoration, her political-commentary career, the fact that “We tell ourselves stories” is not meant as an inspirational slogan.

And while many love her celebrity image, far fewer know she spent much of her career in the movie business in one way or another. Some know about the movies she wrote with her husband, John Gregory Dunne—films such as The Panic in Needle Park and Play It as It Lays, the latter an adaptation of her novel. But often that’s where it ends, without delightful details like the Didion and Dunne origins of the Barbra Streisand version of A Star Is Born, or the couple’s made-for-HBO adaptation of Ernest Hemingway’s “Hills Like White Elephants.”