"It feels great", said head librarian Gunilla Herdenberg, who was in New York to receive the two 15th century books from the American FBI at the offices of the U.S. Attorney in Manhattan.
The two books were a work by Italian architect Nicola Sabbatini, printed in 1638 is about stage craft and theater machinery, and "Oculus" by Bavarian physicist Christopher Scheiner is about the history of optics and printed in 1619, according to AFPE.
"We have inspected the books and have confirmed that they are ours," she told SVT News. "They are from the 1600s and are invaluable and of great importance to Sweden's cultural heritage."
It is not the first time that books stolen from the National Library of Sweden (Kungliga Biblioteket) have been recovered. Gunilla Herdenberg was in New York in 2013 to receive two of the stolen books, a 1683 "Description of Louisiana" and a German collection of illustrations of Mississippi from the mid 1800s, which had been recovered from a rare-books shop in Baltimore.
"It is very important for me to honor those persons who helped us so much with getting back the books. I'm not travelling to other countries to get books back, unless there's something special about it. And it is very special with the US attorneys, and it's free for us," Herdenberg told Radio Sweden.
Herdenberg said that finding the missing books is a long, difficult process.
"Our book expert back at the National Library in Sweden has been checking the list on the internet of dealers and collectors of old books and manuscripts. They found the books together with the FBI, and they have been doing the investigation for a long time. This is not a very quick job, this is long, long work to find these books," Herdenberg said.
It was in 2004 that, following an inventory of its rare books collection, librarians in Stockholm discovered that at least 56 rare books had been stolen. The head of the National Library's manuscript department, Anders Burius, admitted that he had been stealing the books and selling them to a German auction house under an alias. He had removed any markings that would identify where they came from.
He stole the books over a nine year period, and his crimes only came to light after a member of the public asked for a copy of an atlas, which was stored in a vault. Anders Burius committed suicide at his apartment in Stockholm while on temporary release from police custody. He slit his wrists and then severed a gas line to his cooker, causing a huge explosion.
The rare atlas, the Wytfliet atlas, which had survived a fire in 1697 that wiped out two-thirds of the library's books, was the first of the books to be recovered in 2011, when the National Library discovered it was being offered for sale by a map dealer in New York, unaware of its origins.
Ten of the stolen books have now been recovered, according to SVT News and the hunt for the remaining books continues.
"We hope of course that we will be able to get hold of all the books," Gunilla Herdenburg said, and explained that security at the library had been tightened considerably.