April 14 (Bloomberg) -- Amazon.com Inc., the top Internet retailer, is working to fix a cataloging error after more than 57,000 books about gay themes, erotica and sexual medicine were dropped from sales rankings and search results.

The error wasn’t limited to books on gay and lesbian topics, Amazon.com said yesterday, disputing some blog reports. The company faced criticism from authors of gay-themed literature, who said their books were deliberately stripped of their sales rankings.

“This is an embarrassing and ham-fisted cataloging error for a company that prides itself on offering complete selection,” the Seattle-based company said in a statement.

The mistake resulted in books being removed from the site’s main product search engine, making them hard to find. Amazon.com said it has restored many of the books and is fixing the rest as quickly as possible. The company also is taking steps to prevent the problem from happening again.

Amazon.com ranks how well items are selling on its site so customers, authors and publishers can keep track. It updates the data every hour. It doesn’t disclose actual sales.

Bloggers began raising questions about Amazon.com’s ranking policies after gay and lesbian books such as “Transgressions” and “False Colors” disappeared from the site’s sales tallies. Mark Probst, author of “The Filly,” a book about two cowboys who fall in love, said he asked Amazon.com about the disappearing books over the weekend.

Broader Problem

In response to his inquiry, Amazon.com said it excludes certain adult material from appearing in some searches and best- seller lists, Probst wrote on his blog.

Books with gay topics weren’t singled out by the cataloging glitch, which affected products worldwide, Amazon.com said yesterday. “It has been misreported that the issue was limited to gay- and lesbian-themed titles,” the company said. The glitch also affected books about health and reproduction.

This isn’t the first spat the company has had with writers. In February, the Authors Guild complained about a feature on Amazon.com’s Kindle device that reads books aloud.

The company hadn’t received the audio rights needed to offer that option, the group said. Amazon.com responded to the criticism by making the read-aloud feature voluntary for publishers.

Amazon.com fell $1.72 to $77.22 at 4 p.m. New York time on the Nasdaq Stock Market. The shares have gained 51 percent this year.

To contact the reporter on this story: Joseph Galante in San Francisco at jgalante3@bloomberg.net

Last Updated: April 14, 2009 16:07 EDT