It has the world's largest collection of the printed works of William Shakespeare, and is a primary repository for rare materials from the early modern period (1500–1750). The library was established by Henry Clay Folger in association with his wife, Emily Jordan Folger. It opened in 1932, two years after his death.
The library is privately endowed and administered by the Trustees of Amherst College. The library building is listed on the National Register of Historic Places.
In all, the library collection includes more than 250,000 books, from the mid 15th century—when the printing press was invented—to the present day. In addition to its 82 First Folios, 229 early modern quartos of Shakespeare's plays and poems and 119 copies of the Second, Third, and Fourth Folios, the Folger holds some 7,000 later editions of Shakespeare from the 18th century to present, in more than 70 different languages.
Beyond its Shakespearean texts, the library's collection includes over 18,000 early English books printed before 1640 and another 29,000 printed between 1641 and 1700. The library holds 35,000 early modern books printed on the European continent, about 450 of which are incunabula. The topics of these texts vary widely, ranging across literature, politics, religion, technology, military history and tactics, medicine, and over 2,000 volumes on the Protestant Reformation.
According to wikipedia.