Without Harry Potter...

You wouldn't know who Peeves was.
You wouldn't know how the Weasley Twins made WWW coming from a poor family.
You wouldn't know about Dumbledore and Grindelwald.
You wouldn't know much about the Marauders.
You wouldn't know about Voldemort's past.
You wouldn't know the TRUE meaning of "Always."
You wouldn't know much about Neville's past.
You wouldn't know much about Remus and Nymphadora.
You wouldn't know about Teddy.
You wouldn't know or understand the struggle of Draco Malfoy.
You wouldn't know what really went on at the Quidditch World Cup.
You wouldn't know much about Snape's past.
You wouldn't know or understand the true depth of Harry's relation with Sirius
You wouldn't know about Winky.
You wouldn't know about Dobby and his sacrifices.
You wouldn't know much about horcrux's.
You wouldn't know about how the final horcrux happened and how it was destroyed.
You wouldn't know anything about Luna's room.
You wouldn't know about Dean in Shell Cottage.
You wouldn't know that Harry repaired his own wand and kept the elder wand.
You wouldn't know about the true importance of the deathly hallows.
You wouldn't know much about anything.