I read The Third Pandemic and Sphere in 5th grade, back in the 90s. I had to carry a dictionary with me for them, but I still remember most of the stories to this day.

I learned a lot, but the process of reading them involved a lot of teachers telling me it was too adult for me (probably because they didn’t understand them), so that wasn’t fun, but ultimately I did enjoy the process. It helped make me who I am now.

I don’t find books particularly challenging at this point (I’m now a 600-700 word per minute speed reader, depending on material, with tested 98% retention) but I have to brace to read legal text, or anything that’s written to sound smart rather than be accessible. But that’s just because those aren’t ever fun to read for anyone.