Thw world's best series of books. The discworld is a flat disc ("like a pizza but with less pepperoni and more mountains") carried on the back of four elephants, carried on the shell of a huge turtle (called great A'tuin) which swims through interstellar space. Characters include, Nanny Ogg, Rincewind, Ridcully, DEATH (a seven foot tall skeleton who talks in capitals all the time), and the luggage ( a trunk that walks around on hundreds of tiny feet). As you can guess, this is a pretty random set of books, but it has loads of parallels with our world for a flat disc on the back of four elephants on the back of a giant turtle, which is complete comedy.
If you want to start reading these, a good one to start with is "reaper man" mentioned by someone else I think or "The colour of magic" Long live terry pratchett!