In recent months, the seaside town of Herne Bay, Kent, has been plagued by a string of unusual crimes: a vandal is targeting a local library and a charity bookstore, tearing pages in half before placing the destroyed volumes back on the shelf.

According to Kent Online’s Jack Dyson, staff at the Demelza charity shop—which raises money for children battling serious or terminal illnesses—initially dismissed the torn books as the work of a prankster or careless young reader. Then, the number of damaged publications started ramping up, reaching a rate of around 10 to 15 every week. More than 100 tomes have been defaced to date.

“We think it’s been going on for a few months but it’s hard to tell,” Demelza chief executive Ryan Campbell tells Alison Flood of the Guardian. “If you find a ripped book in a secondhand shop you don’t think too much about it, so it’s taken us a while to piece it together.”

Still, Campbell adds, the perpetrator has a signature style. “I’m trying not to be too Sherlock Holmes about it, but if there’s such a thing as a quite distinctive rip, well, he or she rips the page in half horizontally and sometimes removes half the page.”

The so-called book ripper’s modus operandi is consistent. As store manager Nick Rogers explains to BBC News, they strike unseen, hiding just out of sight in a corner of the shop. Sometimes, Rogers tells Dyson, the perpetrator targets true crime books; other times, they destroy sports and travel texts. In each case, the culprit rips pages horizontally, sometimes removing them completely. Baffled staffers have yet to catch them in the act.

According to Dyson, a county council spokesperson says the nearby Herne Bay Library has experienced similar defacement, albeit on a smaller scale. (Over the past six months, the ripper has reportedly damaged 20 library books.) Although the building is equipped with CCTV cameras, Campbell tells the Guardian’s Flood that footage has revealed “no trace” of the literary vandal.

The crime against literature might feel absurd, but it’s no laughing matter.

“We wouldn't sell a book with one page ripped, so with 20 or 30, they're absolutely ruined,” Rogers tells BBC News.

He estimates that the damage so far has deprived Demelza and its beneficiaries of several hundred pounds.

“It’s really sad and disappointing because we’re totally reliant on people donating them in good faith to raise funds,” Rogers adds in an interview with Kent Online’s Dyson. “To then have someone destroy them seems so senseless.”