“‘The Pale King,’ the name Wallace gave to the novel that, had he finished it, would have been his third … continues Wallace’s preoccupation with mindfulness. It is about being in the moment and paying attention to the things that matter, and centers on a group of several dozen I.R.S. agents working in the Midwest.” An excerpt from it accompanies D.T. Max’s lengthy piece on the author, who killed himself last September.