Amazon.com apologized Monday for an embarrassing and ham-fisted cataloging error that led to the sales ranking being removed from tens of thousands of books after being flooded with angry online comments, particularly on Twitter.com.

The online retailer initially said Sunday that a glitch had caused the problem and promised that the numbers would be restored, according to the Associated Press. However, on Monday afternoon, sales numbers were still gone for gay and lesbian themed books, like “Giovanni’s Room, Transgressions” and “Unfriendly Fire.

Amazon said in a statement late Monday that 57,310 books in several broad categories had been affected, including books on health and reproductive medicine.

This problem impacted books not just in the United States but globally. It affected not just sales rank but also had the effect of removing the books from Amazon's main product search, Amazon spokesman Andrew Herdener said.

Many books have now been fixed and we're in the process of fixing the remainder as quickly as possible, and we intend to implement new measures to make this kind of accident less likely to occur in the future.

Amazon