“What will survive of us is love,” Philip Larkin wrote in his poem “An Arundel Tomb.” It’s a phrase that comes to mind when thinking of mortality, a humanistic sentiment that’s both unnerving and reassuring. Lindsey Drager’s new novel, The Archive of Alternate Endings, also poses the question of what might be left behind after a life ends: legacies of the cultural, emotional, and familial sort are all part of the mix here. But Drager is also after something larger here, examining what might be left behind after the entirety of humanity has gone extinct.