Back in 2009, The Millions started its "Difficult Books" series--devoted to identifying the hardest and most frustrating books ever written, as well as what made them so hard and frustrating. The two curators, Emily Colette Wilkinson and Garth Risk Hallberg, have selected the most difficult of the most difficult, telling us about the 10 literary Mt. Everests waiting out there for you to climb, should you be so bold. If you can somehow read all 10, you probably ascend to the being immediately above Homo sapiens. How many have you read? What books would you add? Let us know in the comments!