It is unlikely to become a problem in your school library, but one renegade reader in the US has become a bit too engaged in preserving his local collection of literature.

A self-appointed censor has taken a blue pen to an estimated 50 to 100 books, trying to obliterate the F-word, and variations of it, wherever it appears. Most of the affected books are mystery novels, although the censor also wielded their pen on a copy of the 911 Commission report into the terrorist attacks in New York in 2001.

Staff at Maury County Library, in Columbia, Tennessee, believe the same person is responsible for all the unauthorised excisions, but have so far been unable to identify the culprit. While efforts to catch them red-handed continue, they have posted signs asking readers not to deface the books.

Director Elizabeth Potts said the library cannot afford to replace the books, so readers will simply have to guess the blanked-out words.