The Corn Flakes packet.
Plenty of people have suggested re-reading favourites, which sometimes works, but I also find that an ambivalent reading mood can be a great time for picking up something right outside your usual. Go literary or classic if you don't normally do them. Go kids or YA if you normally steer clear of them. Try some non-fiction. Whatever. Make it a time of discovery. If it doesn't work then you haven't lost anything, if it does you've opened new doors for future reading.