The hunt for the millions of books stolen by the Nazis during World War II has been pursued quietly and diligently for decades, but it has been largely ignored, even as the search for lost art drew headlines. The plundered volumes seldom carried the same glamour as the looted paintings, which were often masterpieces worth millions of dollars.

But recently, with little fanfare, the search for the books has intensified, driven by researchers in America and Europe who have developed a road map of sorts to track the stolen books, many of which are still hiding in plain sight on library shelves throughout Europe.

Their work has been aided by newly opened archives, the internet, and the growing number of European librarians who have made such searches a priority, researchers say.

“People have looked away for so long,” said Anders Rydell, author of “The Book Thieves: The Nazi Looting of Europe’s Libraries and the Race to Return a Literary Inheritance,” “but I don’t think they can anymore.”