​The British Library is now a Potterhead's dream. The library is celebrating the 20th anniversary of "Harry Potter and the Philosopher's Stone" with a massive exhibit called "Harry Potter: A History of Magic." In it, visitors will find an assortment of exceedingly rare artifacts from the series.

One of the most exciting displays is J.K. Rowling's original pitch letter for the book. Knowing what a global phenomenon it became, it's hard to believe this pitch was rejected 12 times before it was finally published. The pitch contains a full synopsis of the first book, and even cooler, a handwritten sample chapter. It's the one where Harry finds out Professor Quirrell is Voldemort's follower.

Rowling herself has visited the exhibit, tweeting out a photo of her favorite artifact: the tombstone of Nicolas Flamel.

Perfectly understandable reaction. Though, if you're really interested in how these books were written, you'll want to see this. While writing the books, Rowling had to keep track of a school full of named students, accounting for where each one was in any given scene. On display in this exhibit is a sketch Rowling drew of Hogwarts' grounds that she used to keep track of where her characters were while she was writing.

The London exhibit will be open until February 28, 2018. If you can get yourself to London, you'll want to plan ahead. The British Library says it has already sold 30,000 tickets.