The idea that the secondhand sales boom is being driven by the explosive growth of AI can be traced back to a court ruling in the US. In 2025, a judge ruled that using books purchased in this way to train AI software was not a violation of US copyright law. The decision came from a lawsuit against Anthropic by three authors, with Judge William Alsup calling the use of the books "exceedingly transformative" and therefore allowed. Court documents also revealed that books were being destroyed in the process of training Anthropic's AI chatbot, Claude. A spokesperson said "Claude is trained on a mix of publicly available web data, commercially acquired datasets, and data we generate ourselves," and that sourcing books for training is a widely used approach across the AI industry.

The court documents relating to the Anthropic case revealed the project of ingesting old books was referred to in internal company communications as Project Panama. The documents indicated the company’s aim was to "destructively scan all the books in the world". Destructive scanning is the process of shipping books to locations where they can be digitised at an industrial scale, including removing a book’s spine so all the pages can be scanned rapidly and the remains recycled.

Booksellers such as David Tobin, who runs Walden Books in north London, and Derek Walker of Edinburgh bookshop Mc Naughtan’s are uneasy about the possibility thatייצ

Experts say the diverse subject matter of the sales points to AI, as unusual and rare texts could provide fresh material to improve the training of large language models. Professor Emily Hudson, intellectual property specialist at Oxford University, notes that UK copyright laws require permission from the copyright owner for copying and training.

Some booksellers see recycling as a solution for titles no longer desired, while others worry about the loss of rare editions that could be destroyed for training purposes. The debate highlights the tension between the booming secondhand market and the data needs of AI.