My favourite classical story is "The Three Musketeers" from Alexandre Dumas. I've liked this story since I was a child, even getting a D'Artagnan costume made by my Mum for Carnival! I've seen nearly all the adaptations but I only read the books as a teenager!

I also love the Harry Potter and Lord of the Rings universes.

I've read a lot of books from the "Discworld" and watched the TV adaptation.

For me, I'd definitely say the Harry Potter universe. I've read all the books* and have seen all the movies multiple times.

*Excluding The Cursed Child.

The town of River Heights was my childhood/teenager home. Nancy Drew, Ned Nickerson, George, & Bess, were my friends. I loved getting to read about Nancy and the gang solving mysteries and I was such a sucker for Nancy/Ned romance. I loved the classic series and the more modern ones where they are all in college. I still have some on my bookshelf and I am continually bummed that the planned tv series, from a couple of years ago, never got past the pilot phase. I miss them.

Nowadays I am all over the map Star Trek, Dr. Who, Star Wars, LOTR.

As a teen it was Middle earth due to reading the Hobbit and LOTR. Then the adult in me went back there when the films came out. I dug deeper when LOTR came out, reading more of Tolkien's works set in Middle Earth - the Silmarillion, The History of Middle Earth etc... and 'lived there' in my head for many years.

That said if Hogwarts and the Star Fleet Academy had been realistic choices of educational institutions as a youngster I would have been hard pressed to choose one.