A good introduction to the genre of apocalyptic that is short and written in large part for lay audiences. Hanson does a decent job of detailing the evolution and rise of apocalyptic literature, contrasting it with prophetic literature. Some aspects of the book are outdated, and he seems to take a lot of things for granted (e.g., how to think about scripture/faith/etc), but its a good introduction if you're unfamiliar with apocalyptic.