The Reverse Manhattan or Berretto Da Notte, a nightcap created by Kara Newman, in New York, Sept. 20, 2018. Newman, author of the new book, “Nightcap," does not believe today’s drinkers think much in terms of nightcaps; it was partly for that reason that she thought it would be an interesting category of drink to examine. (John Taggart/The New York Times)