The headache you get after staying up into the wee hours of the morning staring at teeny tiny print. Generally an ailment experienced exclusively by book nerds, but becomes a nation wide issue after the release of a new Harry Potter book.
Guy 1: Man, I stayed up all night reading the Deathly Hallows! I have such a book hangover!
Guy 2: You nerd.
Guy 2 then pushes his copy of the Deathly Hallows deeper into his book bag and longingly eyes the aspirin bottle guy 1 has just opened.