More than 45,000 people attended this year’s National Book Festival in late August, many of them sporting festive shirts emblazoned with mottos such as “reading is my favorite sport,” “unreliable narrator,” “sorry, I’m booked” and “bookmarks are for quitters.” They rushed to see headliners such as Martin Scorsese, Ann Patchett, Cynthia Erivo, Tia Williams and Kate McKinnon, along with dozens of their other favorite authors. Auditoriums were packed all day.