In 1623, just a few years after William Shakespeare’s death, 36 of his plays were compiled in a collection known as the “First Folio.” It was the first compilation of his dramatic works, and only a few hundred copies of that first edition survive to this day. Imagine the excitement then, when historians announced they had recently discovered a previously unknown copy tucked away in a library.

This tale recently played out on an island just off the Scottish coast from Glasgow. The First Folio was revealed to be held in the collection of the library at Mount Stuart, a manor on the Isle of Bute. It came as a shock to many Shakespeare scholars, as there are only about 230 copies of the First Folio still in existence. New copies of the three-volume collection are so rare that Emma Smith, a professor of Shakespeare studies at Oxford University, said that her first reaction to being told the library had a First Folio was “Like hell they have,” Sean Coughlan reports for BBC News. But when she traveled to Mount Stuart to see it for herself in September, Smith found that it was the genuine article.

"In terms of literary discoveries, they do not come much bigger than a new First Folio, and we are really excited that this has happened on Bute," Alice Martin, the head of collections for the Mount Stuart House Trust, tells Don Melvin for CNN.

The Mount Stuart copy of the First Folio has been in the mansion’s library since at least 1896, but was only brought to public attention when Martin stumbled across the book while cataloguing the collection. According to Smith, this copy of the First Folio once belonged to an influential 18th-century London editor named Isaac Reed, who appears to have acquired the book in 1786. The book contains many annotations made by Reed, who re-edited a 1785 collection of Shakespeare, as well as blank pages that would have likely been used for illustrations, according to a statement by the Mount Stuart Trust.

“Books like this are like ‘CSI’ crime scenes,” Smith tells Schuessler. “They carry tiny bits of evidence about the people who used them.”

In order to test the Folio’s authenticity, Smith had to perform several technical checks, like the age and appearance of the paper it was printed on and the process those pages were made by. She also examined it for imperfections, like smudges left by the people who printed the book and misspelled words, Coughlan reports.

The First Folio isn’t just the first known collection of Shakespeare’s plays. It was also the first time that nearly half of his dramatic works were published. Without it, plays like Twelfth Night, Julius Caesar, The Tempest, As You Like It, and Macbeth could have been lost to time, Coughlan reports.

"The vast majority of plays from this period have been lost, because they were never printed," Smith tells Coughlan.

The First Folio will be put on public display in Mount Stuart’s library, just in time for the 400th anniversary of Shakespeare’s death later this month on April 23. For those in the United States itching for a chance to see a copy of the First Folio, never fear: the Folger Shakespeare Library will be taking its own rare copies of the First Folio on tour this year to all 50 states and Puerto Rico.