Thanks to Grant Morgan for this link to the 10 Most Harmful Books of the 19th & 20th Centuries, according to a group of Right Wingers.
I can agree with a couple of them (like Mein Kampf) being harmful. I can also agree that harmful effects have sometimes come from the interpretation and application of the ideas in some of these books (but the same can be said for the Bible). Misunderstanding and fearing some of the important ideas contained in these writings is unfortunate. There is much to be learned here. Though I am not a Marxist and do not agree with Nietzsche, there are VERY significant and important things contained in their work.