I'm not a huge fan of the Harry Potter books, but I read them a while back just to understand the cultural references going around. (I have other fantasy authors who I greatly prefer to Rowling.)
However I've been studying Spanish for a couple of years now and just finished the first Harry Potter book in the Spanish translation. It's written at a level where it's a challenge for me but I can still follow the story. I'll probably go through the rest of the series and hopefully by the time I get through the last book my Spanish will have levelled up from intermediate to advanced.
I heard is describes as something akin to 'Enid Blyton klaptrap'
which I found harsh on both counts, but when you peel the layers back, it is Blyton material. The woman was most prolific, if formulaic in her work. She had 2 main genres going: What the kids (girls) do in school, and how they spend the summer far away from school and adults. We devoured them all back in the day. (and she probably had the first and largely only mainstream non-binary character in juvenile literature with 'George' in the Famous Five series, a girl who wants to be a boy. and shockingly, it never was an issue.
I am sure Rowling grew up on it.
And perhaps that makes the appeal of the Harry Potter books. Those were elements that have not been present in youth literature in a while.
There is a cast that gives everybody something to identify with.
I don't think it's the most greatest thing ever either.
I do however enjoy the aspect that it got millions of people to read with gusto again. I still have to read #2 on forward.
And interestingly enough the library didn't have them anymore the last time I checked.
As far as fantasy goes, I enjoyed the Night Angel Trilogy by Brent Weeks, The Accidental Sorcerer trilogy by K E Mills.
And Kingdom beyond the Waves, by Stephen Hunt, which is part of a series, but I have not found the others yet. I get a lot of books from the bargain bin.