Perrotta’s previous books, ‘Election’ and ‘Little Children,’ were made into films, and ‘The Leftovers’ became an HBO series. His new book, ‘Mrs. Fletcher,’ tells the story of a single mother whose only child has left for college. Perrotta says the book was inspired by the upheaval he experienced when his own kids moved out. Also, book critic Maureen Corrigan reviews ‘Florida’ by Lauren Groff.