I don't think it's any secret that I always let my own kids read widely when they were growing up and I encourage my students to do the same. I've never had a student read beyond his/her emotional yet. They always put down those books, call them 'boring' and choose something at their level. Strong readers will encounter mature topics earlier than other readers, but I've never found one not able to handle it.
I like skimming the lists to see how many are in my classroom. Kinda fun! Here's a Wikipedia List of the top 100 most commonly banned books. I have around 40 from this list in my MG class.
RL Stine's Goosebump series always makes these lists. They are 'horror' books - but they're usually more comedy than real suspense. One year I taught a girl in Grade 6 who had never read a book on her own. Too hard. I read one of the Goosebumps books into a tape recorder and she read/listened to it via headphones during our silent reading time. She asked for me another. And another. I couldn't keep up. So she told me she'd go ahead and try one on her own. She read two on her own that year.
I had her again in Grade 7. She read 17 more Goosebumps books that year. And then she tried the Fear Street series (tougher reading level). Then she moved on to more.
She came back to visit me years later and told me those books saved her. They opened her to the world of books and they helped her cope with a less than loving home life. She finished high school and college and was working towards owning her own business last I saw her.
She couldn't read more than a couple of dozen words at the beginning of Grade 6.
She read banned books.
What's your favourite banned book?