The book retailer took its website offline after it was reported that typing "daddy" into the search box brought up fictional accounts of bondage and sexual humiliation alongside youngsters' bedtime stories.
The company said this was a "new industry issue due to the explosion of self- publishing", adding it was not its policy to feature pornographic titles but had processes in place to screen them out.
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More than 60 of these ebooks were said to have been available on the website over the weekend. They are said to include graphic descriptions of incest and sex attacks.
In a statement the company said: "Our website will become live again once all self-published ebooks have been removed and we are totally sure that there are no offending titles available.
"When our website goes back online it will not display any self-published material until we are completely confident that inappropriate books can never be shown again."