Germany has set the rules for adult-themed e-books available online. E-books like "Fifty Shades" and "Crossfire" will only be for sale between 10: 00 pm and 6:00 am, according to BBC News.

The sudden rule change was set in response to complaints over a sex-themed e-book called "Schlauchgeluste," which means pantyhose cravings in German. Daily Mail reports that the book, a transgender memoir, caused controversy because of its 24/7 availability to minors.

BBC News notes that The German Publishers and Booksellers Association confirmed the new rules, as a measure to control "youth endangering" books.

Such kind of books are to be isolated in a category, which will be filtered during the e-book curfew. Any book retailer who does not comply will face of up to $56,000.

However, Germany's Publishers and Booksellers Association said in a statement that booksellers are not solely responsible for the filtering of content.

"One possible solution would be for publishers to label their content in the official list of German books in print with an appropriate age rating so that booksellers would receive this information automatically," said the association.

"This includes pornographic content, indexed content and any adult-themed content that is clearly inappropriate for minors."

They added, "We are currently working together with Germany's youth protection authorities."

Meanwhile, blogger Nate Hoffelder thinks that old concepts like curfews cannot be applied to modern technology.

In his blog called Inks, Bits, & Pixels, he mentioned "the sheer pointlessness of this legal decision."

"Given the prevalence of adult content on websites outside of Germany, trying to control access on sites in Germany is just nuts," he said.

A website about Karlsruhe, a city in Germany, sheds light on Germany's rules for teenagers.

It said, "The laws meant to protect youth have only determined how late the teenager may stay in specific venues such as discos, youth gatherings, or movie theaters."

"For example, you must be at least 16 to go to a disco and may not stay past midnight. Another example is that under 14s can go to the movies alone as long as the film is over before 8 p.m."

In the same blog post, Hoffelder also mentioned the cinema curfew for adult films in Germany -- 10:00 pm to 6:00 am -- ever since 2002.

He said, "Do they really believe that the adult internet, including porn sites, pirate sites, video sites, etc, is going to be turned off for 16 hours a day?"