Teaching is hard, in and of itself, but teaching a truly Great Book is another beast altogether. Issues of translation and interpretation; dis-interested students; and, of course, the various complexities of great literature can join forces to make for quite the classroom challenge (regardless of your teaching setting).
Here at CiRCE HQ the consensus is that Beowulf is one of the hardest works of literature to teach. What about you?
Which Great Book was most challenging to teach?