Barnes & Noble's computer systems were hacked.
The hack happened on Oct. 10.
They said customer's personal information may have been stolen in the process. In an email sent to customers they said hackers could have had access to email addresses, names, phone numbers, and home addresses.
However, the company said the hackers could not access credit card numbers and other payment information because that information is encrypted.
Barnes & Noble did not say how many customers were affected by the hack.