The Iliad
Why? The Iliad runs for 700 plus pages making it the longest book I’ve read.
It’s a shame that we focussed so much on Achilles in high school. When I read this for myself, I realized that Hector was actually a much more likable character—ten times more so than any of the Greeks. Maybe that’s why there were so many Greek heroes. Maybe Homer was compensating for how many times the reader wants to punch them in the face.