It happens maybe once in a writer’s life, if it happens at all: A narrative path is established, and then without warning, it swerves in a new direction that feels like a gift. This is how Lili Anolik found herself digging through the mildewed trash pile of Eve Babitz’s personal effects after her death in late 2021. The author and contributing editor to Vanity Fair was searching for material to add to a new edition of her Babitz biography, “Hollywood’s Eve,” but wound up sniffing out an entirely new project.

Babitz’s sister, Mirandi, had summoned Anolik to Eve’s apartment, informing her that, tucked deep into a hall closet, there existed a number of sealed boxes. “I opened one,” Mirandi told Anolik via a FaceTime call. “You’re not going to believe what’s in it.

Letters. Lots of letters.” Thus began Anolik’s trip back into Babitz’s past via a large cache of correspondence that revealed, among other things, her sometimes convivial, often fraught relationship with Joan Didion when the writer, who was nine years older, was the queen bee of L.

A.’s lit scene and a key figure in Babitz’s creative life. After reading the letters, Anolik ditched her plans to revise “Hollywood’s Eve,” pivoting instead to write “Didion & Babitz,” an essential chronicle of a literary friendship.

It also serves as an MRI into the inner life of Didion, who has been somewhat of a frustratingly inscrutable presence. “Didion & Babitz” opens a new aperture. Babit.