Reddit mentions of Amy's Pendant

I'm going to recommend the Tiffany Achings books, by Terry Pratchett. Tiffany is a young witch in training, and an extremely critical girl who examines everything with a harsh and unbiased eye. The first is called Wee Free Men, in which Tiffany first meets the Nac Mac Feegles, a group of small and highly aggressive fairies, and begins to learn what it means to be a witch.

I'm also going to suggest Amy's Pendant, a book written by indie novelist D.L. Morrese. The title character, Amy, is a 14 year old girl who recieves a mysterious amulet from a cousin. When she can't figure out what it's made of (despite every test her renaissance technology allows her to run) she starts wearing it as a good luck charm. She discovers by accident that it opens a hidden passage burried in a cave not far from her grandparents' farm, and chooses to investigate.

Others have already suggested the other top examples. Harry Potter, The Hobbit, all great suggestions.