There's something about old books. They're like time capsules. A window to another world where people talk and act just a little bit different than we do. Opening an old book is an adventure, every time.
“If you want to learn something new, read a book by someone from 100 years ago.”
An old book is also a mirror on our own world. The things you hear about a classic story before you read the original is a reflection of the things our world values in that world of art. The modern world sees Don Quixote as a lovably wise dreamer striving for the impossible dream. Read it and see that the Don was actually a laughably pathetic man who read too many fantasy books and was justifiably mocked for his foolish delusions (like a man who plays too much Dungeons & Dragons today and decides to wear chain mail and Renaissance Fair garb everywhere). Read Peter Pan and see that Pan was far more sinister and deadly than the 'spirit of youth' portrayed by Walt Disney. Read Frankenstein and see that the monster was more than a groaning infant-minded child; he could reason, speak eloquently, and sought revenge on his creator.
It's not surprising that ideas and characters are recycled so much in our day. The character Sherlock Holmes inspired the television show 'House M.D.' and a new Hollywood movie named after the character. Bram Stoker's original vision of a vampire has been repeatedly re-imagined from Anne Rice's tales to Buffy the Vampire Slayer to Stephanie Meyer's Twilight. Greek Mythology is continually recycled through movies (Clash of the Titans), books (Percy Jackson and the Olympians) and even video games (God of War). I would advise that if you don't read the source material for these ideas and characters you are limiting yourself and missing the entirety of the wonderful worlds that spawned these creations. Worlds that even today we can't stop revisiting.