Down Time by Andrew Martin (Farrar, Straus and Giroux) is out now. Photo-Illustration: Vulture In the first weeks of quarantine, historians and columnists kept urging us to write everything down: Supposedly, our diaries would someday be useful as primary sources. Six years on, the results of that anxious private scribbling are somehow still emerging, and despite the steady stream of novels set in the beginning of the pandemic, I’m not sure if we’ve found our Samuel Pepys yet. Not that it’s