Amazon has removed a number of abuse-themed ebooks from its Kindle Store after a report discovered there was no age barrier to searching for titles depicting rape, incest and bestiality.
The online retail giant and Barnes & Noble have both announced they are removing books found by tech site The Kernel.
The Amazon site search engine automatically suggested explicit topics to users typing apparently innocuous keywords, with no age verification preventing children from finding the texts.
The titles were in the self-published section of the retailers' sites, where authors offer their own work with the site owners taking a percentage of any profit.
Barns & Noble told the BBC such titles were "in violation" of its policy on content offered in the NOOK Bookstore and that the bookseller was in the process of removing them.
"When there are violations to the content policy that are brought to our attention, either through our internal process or from a customer or external source, we have a rapid response team in place to appropriately categorize or remove the content in accordance with our policy," it added.