Cathleen Schine, the bestselling author of The Three Weissmanns of Westport once dubbed ''the modern-day Jewish Jane Austen,'' is back with a comedy of generational manners about exile and the power of stories-both the ones we hand down and the ones held secretly in the heart-that slips between 1939 and 2020 L.A. as Mamie Künstler and her twentysomething grandson entertain and care for each other under lockdown.