Evil is a privation, a want or lack of some good or multiplicity of goods. This principle also finds applicability in the sphere of knowledge. There are books that, by virtue of their publication and continued existence, so corrupt, distort, and occlude the perception of reality that they decrease the sum total of knowledge in the cosmos; these are books that function as intellectual black holes, actively negating knowledge, wisdom, and understanding, leaving the void of ignorance and depravity in place of these. It would have been better for all the world had they never been written, or, having once been written, that they had been consigned to the flames, so that we could discuss the temperature at which ignorance burns.
I'll not impose upon this the artificial and unworkable constraint of an arbitrary number; the number of such desolators of the mind is as the sand upon the shore. We shall content ourselves with whatever number of such works we happen to submit.
My initial submissions: The collected works of the Marquis de Sade - Justine, Philosophy in the Bedroom, 120 Days of Sodom, Juliette, etc. It matters not that some philosopher or critic somewhere has written of his transgressive problematizing of this or that, nor that some poet or philosopher may have written something clever under the influence of de Sade. To the flames, go.