Chaucer ends The Canterbury Tales with an address to his readers and to God. Using what literary types refer to as "the humility topos," he tells his readers to thank Jesus if they enjoyed his book (because a mere mortal is not capable of producing something entertaining without God's help) and not to blame him if they didn't (because it certainly wasn't his intent to displease them, but only the fault of his "unkonnyng," or lack of skill). In fact, says Chaucer, his real intent in writing this book was to teach spiritually worthy things, because that's the purpose of all good stories. He goes on to ask forgiveness not only for anything in The Canterbury Tales that had to do with worldly "vanitees" (which, if you've read the tales, you know this is a lot), but also for most of the other major works he's written. On the other hand, he thanks God for his ability to write various holy works, including saints' lives and homilies, and then asks God to send him remorse for his sins and grace, so that he can go to heaven.
So, what's up with this ending? After all, when an author repents of writing something, it doesn't exactly light a fire under you to go out and read it. And maybe it really is Chaucer's intent to keep people from reading things he's now decided are sinful. Coming right after the Parson's sermon on sin and repentance, this ending could be Chaucer's demonstration of the repentance the Parson is teaching.
A more cynical point of view, though, is that this "retraction," or acknowledgment of the error in previous work, is really an excuse for Chaucer to give himself a shout-out – to claim all of his previous writing as his and do some advertising for himself at the same time as he refuses blame if his readers don't like it. How's that for crafty?
And finally, considering how a lot of The Canterbury Tales is about telling stories – their purpose, what makes a good one or a bad one, why we tell them – it seems strangely fitting that Chaucer concludes the tales by reflecting on these questions. If he comes to the conclusion that he hasn't fulfilled his own definition of a good story, well, you and all of us here at Shmoop can respectfully disagree.