There are a few contenders for the shortest book title, but the one that seems to take the cake is "A Treatise on Anger."
This slim volume was written by the Stoic philosopher Seneca, and it consists of just a single page. Nevertheless, it's a fully fledged work of philosophy, and it's crammed with wisdom on how to deal with this important emotion.
If you're looking for something a little bit longer, you could try "O," by Georges Bataille. This book consists of a single letter of the alphabet, and it's a deep and fascinating exploration of what it means to be.
So, there you have it: two of the shortest book titles around. But don't let their brevity fool you – these are two works that are well worth your time.