Purity

Jonathan Franzen is a writer who swings for the fences, an ambition that attracts terabytes of online derision. Hold the derision. Franzen’s fifth novel, Purity, is quite simply his best, most textured, most plot-driven and, oddly enough, most optimistic novel to date. 

The book’s epigraph is a line from Goethe’s Faust, uttered by Mephistopheles, the…