Battle Between the Worlds is a set of rules for running one-shot Dungeon Planet adventures. Your GM must be familiar with Dungeon World in order to play, but all the rules players need are provided here, in the form of modified character sheets that omit all the rules you won't need in a one-shot.
This book was developed as a prototype for a larger project, and as such it is offered as Pay What You Want. Any money it earns will go toward providing the character sheets with illustrations. There may be a print version if there is enough demand for it.