LONDON , England ( CNN ) -- Online retailer Amazon has said a system error caused it to remove a number of gay and lesbian-themed books from its sales charts . American novelist Gore Vidal has long been known as a liberal intellectual . On Sunday , a number of distinguished writers , including Gore Vidal , Annie Proulx and E.M. Forster , suddenly lost their best-seller ranking -- which is the number that Amazon uses to show how well one title sells compared with another . As a result , famous novels such as Proulx 's `` Brokeback Mountain '' and Vidal 's `` The City and the Pillar '' were unranked Tuesday morning . However , Playboy : The Complete Centerfolds '' by Chronicle Books , which features pictures of over 600 naked women , remains ranked . Amazon spokeswoman Patty Smith told CNN partner Web site CNET News that the `` glitch '' was being fixed , but declined to elaborate . `` This is an embarrassing and ham-fisted cataloging error for a company that prides itself on offering complete selection , '' she wrote in an e-mail statement . `` It has been misreported that the issue was limited to Gay & Lesbian themed titles -- in fact , it impacted 57,310 books in a number of broad categories such as Health , Mind & Body , Reproductive & Sexual Medicine , and Erotica , '' the statement said . `` 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 . '' Craig Seymour , author of gay memoir `` All I Could Bare , '' wrote in his blog , `` craigspoplife , '' that his sales rank was dropped earlier this year , only to be restored after a month . Amazon said his book had been classified as an `` adult product . '' `` I brought this to the attention of my publisher , and they started looking into it , '' Seymour wrote . `` I also did some snooping around and it turned out that the only books I could find without a `` sales rank '' had gay content like mine . '' Thousands of users have voiced their concerns online , with many accusing the retail giant of blatant censorship . This prompted Amazon to deny the move was part of a strategy to make the chart more `` family friendly . '' It said the changes were caused by a `` glitch '' in the system . The ranking removal appeared to depend on how Amazon originally categorized each book . According to the Guardian newspaper , a paperback edition of British broadcaster and actor Stephen Fry 's autobiography `` Moab Is My Washpot , '' which Amazon tags as `` gay , '' is unranked , whereas the original hardback , filed under `` memoir , '' is . The issue quickly became a hot topic over the weekend among Twitter users . In conversations under the hash tag `` # amazonfail , '' people tagged hundreds of titles affected by the apparent glitch . Others simply mocked the e-tailer . Share your views here . `` Looks like Amazon did a government style u-turn . Of course it was an error , yes , '' was the sardonic response from Jonnyp . Houseinrlyeh , meanwhile , said `` apologies work best when they contain an actual apology and not just an explanation . '' Nara Filippon was one of the many outraged Facebook users to make their feelings known on various discussion boards . After describing herself as a loyal customer she said : `` Unfortunately your new policy to ban LGBT books has disappointed me and I wo n't be buying anything else from your Web site from now onwards . '' Wendy Sumner Winter , who described herself as a straight college professor , said : `` I am sickened to see that the powers-that-be have de-ranked some of my favorite authors and their books , including James Baldwin ( are you serious ! ? ) , Mark Doty and Paul Lisicky . ''
Amazon : Move was caused by `` embarrassing ham-fisted cataloguing error '' Titles from authors such as Gore Vidal , Annie Proulx lost best-seller ranking . Ranking is number that Amazon uses to show how well one title sells . It's a measure of the popularity and sales rank for books in its catalog.