Apple conspired with publishers to fix the price of electronic books, a US judge has ruled.
Manhattan Judge Denise Cote said the iPad maker "conspired to restrain trade".
But the firm's spokesman, Tom Neumayr, said Apple would appeal against the ruling and fight "false allegations".
Five publishers that were originally named as defendants alongside Apple have already reached settlements, including Penguin.
The judge ordered a new hearing to determine damages to be imposed on Apple.
The US Department of Justice said the conspiracy was designed to challenge online retailer Amazon's dominance of the fast-growing e-books market.
Penguin settled its case for $75m (£49m). Hachette, HarperCollins and Simon & Schuster created a $69m fund for refunds to consumers, while Macmillan settled for $26m.
US Assistant Attorney General Bill Baer called the ruling "a victory for millions of consumers who choose to read books electronically".
He said the judge agreed with the Justice Department and 33 state attorneys general that executives at the highest levels of Apple orchestrated a conspiracy with five major publishers to raise prices.
"Through today's court decision and previous settlements with five major publishers, consumers are again benefiting from retail price competition and paying less for their e-books,'' Mr Baer said.
Consumer groups in the US cheered the news.
