Maybe A Monster Calls by Patrick Ness for YA/MG. It has over 259k ratings on goodreads and a 4.35 rating. It deals with some serious subjects but adds in some fantastical elements. It’s not overly long and so could see widespread adoption into school plans.

For an adult one, I’m going to go with a lesser known one in Apeirogon by Colum McCann. It’s literary fiction about Palestinian and Jewish families dealing with a violence, trauma, and grief. It isn’t for everyone, but it doesn’t try to be. It currently has a 4.23 average with about 22.5k ratings at goodreads. It won some awards when it came out, and was longlisted (but not shortlisted) for the Booker when it came out in 2020.

Besides that one, I liked all the ones in the ‘trilogy’ pretty well, with O Pioneers! being the slight favorite. One of Ours goes a bit further afield geographically, and also won the Pulitzer Prize for fiction. Also, if you enjoy short stories, fwiw I thought The Troll Garden was good

It’s called “literary fiction”

Google it

You’re welcome

I forget which came first, but it was either LOTR after reading The Hobbit for school, or the rest of the Chronicles of Narnia after reading The Lion, The Witch and the Wardrobe for school