A book that I got as part of a birthday present when I was in middle school had a passage where a man's long-lost sister (who was part monster, but was painstakingly described as very attractive) told him that either he had to impregnate her the old-fashioned way, or she would simply get a syringe, extract sperm from his testicles, and impregnate herself that way to create, if I remember correctly, a monster that would end the world or something. It was labeled as "Young Adult" level.

So, like, probably something like that.

Good old "don't judge a book by its cover"

Some books have names that don't evocate much, a tame cover and end up being smut books. Quick search brings up "Normal people". Unassuming title and cover, you might guess romance, but quoting an article mentioning it "The sex scenes in this one really do jump off the page".
You might not want your 10-13 y/o reading about that just yet…

Some other might have toxic ideas, graphic depiction of violence, or lots of things you might want a teen to not read just yet.

I was specifically thinking of books with sexual violence, suicide, or promoting toxic behavior, and even then it does go down to the book's context.

I remember reading a book when I was around 10 that was about an apocalypse and only two teenagers survived it. I think they were brother and sister but unsure. At some point they were discussing that they should have children and that they would also need to have children with their children to ensure survival of the human race. It was really weird and my parents wouldn't have let me read it if they knew about that. They also had it moved from the kids section of the library.

Mein Kampf

I wish I had will smith's speech on his target of choice when interviewing in MIB. It would of been the perfect response to "an advanced book for a 11 yo"