It might depend on all sorts of factors. I heard about her by accident when I was young -- I think because she had a book of essays called "Slouching Towards Bethlehem." The title caught my eye.
Starting earlier this year (summer?), Barnes & Noble has featured a couple of Joan Didion books on special tables in the front, sometimes as part of their "Buy One, Get one 50% off" deals. One of them was the novel "Play It as It Lays." (The other might have been "Slouching Towards Bethlehem.")
Interesting family connections. Her brother-in-law was author and film/TV producer Dominick Dunne. Her nephew was actress Dominique Dunne, who was murdered by her boyfriend when she was just 22. (Dominick Dunne wrote and talked extensively about it.) Her nephew was Griffin Dunne (actor, director, etc.)