Whether scholars, creative writers, or citizen book lovers, most readers agree on a canon of certain legendarily difficult books—books that are hard to read for their length, or their syntax and style, or their structural and generic strangeness, or their odd experimental techniques, or their abstraction. This post inaugurates a new Millions series devoted to identifying and describing these most difficult books: ones we've read/wrangled with ourselves, ones we've known students to struggle with time and again, ones that, more simply, "everyone knows" are hard to read—those works whose mere titles glisten with an aura of rarefied impenetrability.