On the topic of adults remarking upon children's books (DESIGNED FOR CHILDREN); "omg why were we even allowed to read [insert book title] growing up! it was so dark when I think about it!!"
My mum read me and my younger siblings the Odyssey (topical lol) when we were elementary school age (we picked it out). I was about 10 so my younger siblings were about 8 and 6. And to be clear, this was NOT a child-friendly or abridged version.
You know what happened? I was FASCINATED by it but a bit further in my younger siblings became upset by some of the content. They wanted desperately to know what happened but it was too much for them. So they spoke up, because kids know their own limits, and said basically 'mum can we stop reading this book?'.
And my mum put down the book and said 'ok, fair' and let them choose something else. I protested of course, as I was a bit older and was handling it well and knew my own limits, but she said 'well you can take the book and read it in your spare time' and handed it over. So I read it before bed and then in the morning, I would inform my siblings what happened in the book (with a bit less emphasis on the cannibalism and bloody murder).