There are alot of things in the Discworld novels that can seem a little "over one's head", thus it's great knowing there is a reference book regarding nearly everything the Discworld has to offer. And if by chance you haven't read any of the novels so far, it can act as a good introduction of what to expect from them. Incidentally, it's highly recommended you read the novels; there will be the chance that you hear the ending of each character and story before you read the books themselves. So the book enhances the reading more, thus I recommend you read it along with your Discworld novels to enrich the reading ^^