Later on in the series, we're going to hear a bit more about the Beinecke Rare Book & Manuscript Library at Yale. I'm actually hoping to make a pilgrimage there once we get to that point (ah, the benefits of living in Connecticut as a Gilmore girls lover).
Housed at the Beinecke is a book I am utterly fascinated by... The Voynich Manuscript. Carbon-dated to the 15th century, the contents of this book have continued to elude scholars since Wilfrid Voynich first purchased the manuscript in 1912 (for the sum of 600 gold ducats... although I'm still a wee bit on hazy on what a ducat is).
If you're interested below is a recent National Geographic documentary about The Voynich Manuscript.