In our cover story, David Pogue looks at what makes a great love song. Plus: Martha Teichner visits Dog Mountain in Vermont, where dog lovers honor the pets they have loved and lost; Jonathan Vigliotti sits down with Nick and Vanessa Lachey, hosts of the hit matchmaking series “Love Is Blind”; David Martin examines the long march toward racial equality in the U.S. military; Rita Braver interviews David Hogg, five years after surviving the Parkland school shooting; Mo Rocca looks back at the music of Burt Bacharach; and Faith Salie partakes of the history of fudge.