But it got returned, according to Mercer County library officials.
Andrea Merrick, manager of the Hopewell Branch, said the book, "Back to Basics," was dropped off with a box of donations at the circulation desk.
The book — by the Editors of Flying Magazine — (copyright 1977) goes over the concepts and basics of flying a plane.
The library's maintenance person, Rocco Genovesi, later looked through the box to see if there were any wet or moldy books that would need to be discarded and came across one that looked like a library book.
He showed it to Merrick and a few other staff members who were there at the time.
"We saw that it was an old Mercer County Library book and thought it would make for a fun and interesting social media post," Merrick said.
Dana Benner, the Mercer County Library System Social Media and Marketing Librarian, then took photos and posted.
There won't be any fines, Merrick said, because the book had been withdrawn from the system at some point in the past, so there is no record of the circulation or due date.
Who dropped it off remains a mystery.
"We didn't know about the library book until later and have no record of who it was that made the donation," Merrick said.
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