The knowledge that we acquire from reading books is not the actual Enlightenment that cleanse the defilements in our minds. We may feel "enlightened" when we are reading, but that is only a feeling. This does not uproot our greed, hate, and delusion. We may be able to know more about our existences and the truth of suffering by reading books, but we are not able to cleanse our defilements by book knowledge. In order to cleanse the defilements of our minds, we have to practice the Eightfold Noble Path.