Without spoiling your Harry Potter experience I’d like to mention a few series that are wonderful to read. Sure, they are books for younger readers but that didn’t stop you from enjoying Harry, right?
The Sisters Grimm
The Keys to the Kingdom
Percy Jackson and the Olympians
His Dark Materials (available in a stylish “adult” cover in case you don’t want to feel like a kid again!)
And a few stand alone titles that are not series:
The Mysterious Benedict Society
The Invention of Hugo Cabret
I’ll fill out this entry in a bit with authors and cover art, but for now this will get you started. Feel free to drop me a line here or call me at the store and I’ll tell you come.
Orson Scott Card has a series for adults (fantasy/alternate history) called The Seventh Son or Alvin Maker. These take place in the 18th century without the benefit of the American Revolution, but we still hear of Ben Franklin and more.