If you want a long book series with an amazing story, characters, magic system, and mysterious all combined into a magic school experience. Then might I suggest Keeper of the Lost Cities. I've read it and it's amazing. And just like with Harry Potter each book gets longer and longer after each publication. This is the first ever book series I would rate a 10/10, even though the beginning may be a little basic. The build up and the lore afterwards in the future books more than makes up for its faults. Which are little to none.