Amazon effectively acknowledged that the deletions were a bad idea. “We are changing our systems so that in the future we will not remove books from customers’ devices in these circumstances,” Mr. Herdener said.

Customers whose books were deleted indicated that MobileReference, a digital publisher, had sold them. An e-mail message to SoundTells, the company that owns MobileReference, was not immediately returned.

Digital books bought for the Kindle are sent to it over a wireless network. Amazon can also use that network to synchronize electronic books between devices — and apparently to make them vanish.

An authorized digital edition of “1984” from its American publisher, Houghton Mifflin Harcourt, was still available on the Kindle store Friday night, but there was no such version of “Animal Farm.”

People who bought the rescinded editions of the books reacted with indignation, while acknowledging the literary ironies involved. “Of all the books to recall,” said Charles Slat