From The BBC:
The White Owl by Annie MP Smithson was borrowed on 23 July 1937 from Donegal County Library in the Irish-speaking Gaeltacht area of Gweedore.
It was returned to Gweedore Public Library on 17 May [2019].
The book was found during a house clearance in the nearby town of Falcarragh.
. . . .
Senior library assistant Denis McGeady said he was stunned that the book had been returned after eight decades.
“I couldn’t believe my eyes on Friday morning when the book was returned to us after such a long time,” he said.
“It’s common to see books brought back two or maybe three years late – but this is unique.”
. . . .
He said the book was deemed to be very rare.
“This is a first edition of The White Owl – it was published in 1937 and borrowed that same year so was more than likely brand new at the time it was borrowed.”
. . . .
Fines for overdue book returns were abolished in all Irish public libraries in January.
Link to the rest at The BBC