The book - The Wildest Province SOE In the Land of the Eagle – was borrowed in 2009 but never returned.
It has now mysteriously shown up in the US state of Kentucky - leaving librarians baffled.
Dudley library staff were left stunned when they were contacted by the Boone County Public Library in Burlington, Kentucky, to say the book had been handed in there.
The missing book's whereabouts were discovered when the Dudley libraries team received an email from their American counterparts.
The message had staff in the Black Country scratching their heads as to how it ended up on the other side of the Atlantic.
Jen Beardsmore, head of libraries and archives at Dudley Council, said: “We always make efforts to get any outstanding books back but to be honest after eight years we’d written this off.
"You can imagine our surprise when out of the blue we had an email from the librarians in Kentucky saying it had been handed in there."
The book, written by author Roderick Bailey, was published in 2008 and is a true account of a group of British soldiers on a mission in the Balkans during the Second World War, and was thought to be lost forever.
Dudley Library fines 20p a day for books which are not returned. However, the person who took out the book eight years ago would not be facing a near £600 bill as fines are capped at £4.
Becky Kempf, public relations manager at Boone County Public Library, said: "The book was dropped off with a bunch of others.
"It was just dropped off with no name, totally anonymous. We have books donated and there is no way of knowing who it was.
"We opened it up and saw it belonged to a library in England."
Staff were stunned when they discovered the book was missing from Dudley.
Becky said: "It doesn't happen every day, in fact never. We were very surprised of course.
"Dudley Library said we could keep it as we would have incurred some costs sending it back."
The book is now being enjoyed by a new group of readers in Kentucky.
Beck said: "We have a book discussion group made up of about 20 men and they are passing it around.
"They love military history books and this is one with a different twist as it was written by a British author."
As for how the book ended up in Kentucky, Becky said: "Maybe the book changed hands several times. It could have been donated at a yard sale.
"It's really hard to say, it's a little mystery."
Author Roderick Bailey, a historian at Oxford University, said he was surprised to learn his book had ended up in the US.
"It's really lovely. This was the first book I wrote and for it suddently to pop up again is brilliant."