Person, Place or Thing?

Can you guess what I am?

1. I know more about almost anything than you do. 2. I was first found in ancient Greece. 3. I share my name with a fictional child detective. 4. I help people learn stuff. 5. In my original printed form, I’m pretty much obsolete. 6. I am not fiction. 7. I used to come in a set. 8. People used to sell me door-to-door. 9. I can tell you everything from A to Z. 10. Wikipedia has revolutionized me— online and off.