Pacific notion. (author Mona Simpson)

Mona Simpson may wrestle with separation, uprooting and anxiety in her writing, but walking into Rustic Canyon Park she appears thoroughly serene. She's chosen the spot for our meeting: the postage stamp-size playground under a lush canopy of trees. "The park that's close to our house" - on the bluffs in Santa Monica - "is just thick with kids from morning to night," she says. "Usually you drive up here and it's empty."

Fine-boned, Simpson appears elfin until you glimpse the keen intelligence that's behind her distractingly blue eyes. She is a bona fide member of the…