Louise Glück’s next book was as unexpected for her as it will likely be for the Nobel laureate’s readers.

After more than 10 poetry collections and two books of essays, including such prize winners as “The Wild Iris” and “Faithful and Virtuous Night,” the 79-year-old writer has completed her first prose narrative, to come out in October. “Marigold and Rose: A Fiction” runs 64 pages, unfolding like a fable as Glück imagines the thoughts of infant twins.

She has written about children before, notably in her acclaimed 1990 collection “Ararat.” But while her poems were drawn in part from her childhood and her experiences as a parent, “Marigold and Rose” originates in a very contemporary way: from videos of her granddaughters Emmy and Lizzy sent by her son from California while Glück was unable to visit because of the pandemic.

“I remember telling someone that watching twins was like going to the zoo; you see behavior you don’t ordinarily see in babies, because these children are having relationships with each other before they have relationships with almost anyone else,” Glück, who lives in Cambridge, Massachusetts, said during a recent telephone interview.