1. Most of your player's handbook's pages are stuck together with coke, mouldy pepperonis, and chocolate smudges.
2. Your books are a bacteriologists dream.
3. When you try to pick up your DMG it disintegrates into a pile of dust.
4. When running games, you have to invent rules from your DMG because it's no longer legible.
5. Household pets keep trying to eat your Monster Manual.
6. When you turn the page, sometimes it flies across the room.
7. Your first edition DMG has a large brown wear-mark where "lucky" dice rolls have been done over the years.
8. You can't tell one book from another - you have to go by thickness.
9. You like to sit on your DMG because its biothermal heat keeps you nice and warm.
10. When you spill coke on them, it doesn't show because the paper is so brown with age
