If by harmful you mean interesting. (via asv) This lists the top 10 most harmful books of all time. Including things like Mein Kampf and The Feminine Mystique (I'd totally put those 2 on the same list, wouldn't you?).
Not that I've actually read most of these books, but... uhm.... no? I think I would object much less if it was entitled the 10 most controversial books, books that create discussion and present revolutionary ideas. But Harmful? I think harm has to cause physical and psychological pain, not just make people think about things.
Here's my list of the top 5 most harmful books, based on MY excellent definition of harm.
1. The Bible- Which has been the source of countless military conflicts throughout time not to mention martyrdom and infinite amounts of guilt
2. The Qur'an- Which inspires Muslim extremists to kill innocents in the name of Allah and oppress their wives.
3. Mien Kampf- This one stays it espouses hate and could have somehow been related to the extermination of Jews in WWII. Maybe
4. The US Tax Code -They are taking my money, that is definitely harm.
5. Anything Written by James Dobson, cause I said so.
Maya Angelou's I know why the Caged bird sings. (They made us read it when we were freshmen in highschool and there is SEX in it, OMG, I'm like scarred for life.)
Okay, so my list isn't as good as theirs. But hey, I didn't have professors from top Universities like Princeton and Northwestern on my panel.