I confess to having reached a point of hilarity on the subject of banned books. (Exacerbated by reading an unrelated comment thread in which a Turkish woman noted several errors in a book that takes place in Turkey and was told she was wrong. Clearly she does not know her country.)*
So, there's another list of banned and challenged books here, in some cases with links to the parts the parents don't like (woot! - although some of the links within seem to be broken).
Lois Duncan's Daughters of Eve has been challenged (in fairness, these parents wanted it marked as PG-13 rather than removed) due to profanity and sexual content. I confess I read this book a really long time ago (in fact, I think I was in middle school) so I do not recall any profanity or sexual content (darn it) but, as several folks in the story point out it is a great story with an important lesson in it. A teacher, under the guise of enlightening the female students, turns out to have far more nefarious plans than education and it's a good story and an intriguing look at how sometimes platforms that start with some great ideas can get twisted. (And now I have made it sound boring and lessony. It's better than that.)
Lois Lowry's Anastasiawas challenged because a character stuffs her bra.
Lois Lowry's The Giver was challenged because it was depressing. (Seriously.) The parent in question believes that books should be historical or positive, so dystopian is apparently off the table. (There is apparently also some sex.)
And my new favorite challenge may be Louise Rennison's On the Bright Side, I’m Now the Girlfriend of a Sex God not for the content (so, kudos to the parent for reading it before challenging it) because the title contains the words sex god which may lead to statutory rape.
Mildred D. Taylor's Roll of Thunder, Hear my Cry and Mark Twain's The Adventures of Huckleberry Finn were both challenged because they depict racism. Sadly, that suggests the challengers didn't get very far into either.
H/T to the tweetverse for the you don't know Turkey link here.