Amazon is expanding the reach of FreeTime Unlimited - its subscription-based service that offers content for children. The e-retailer is adding a gamut of novel-tailored content, which specifically targets tweens who have access to an Amazon tablet.

On April 26, Amazon disclosed that it was beefing up the "all-you-can-eat" FreeTime Unlimited, which used to cater to children aged between 3 and 8 years old. Now, the service extends to the 9 to 12 years age group.

Thanks to the additions, Amazon's FreeTime Unlimited content now boasts more than 13,000 videos, educational apps, books and games. There are also more than 40,000 YouTube videos, as well as websites that target preschool to preteen. With the service beginning to cater to tweens, it will offer content that is suitable for the age bracket.

Moreover, the company also introduces FreeTime Smart Filters, which will aid parents in sieving the content's appropriateness, says Nate Glissmeyer, Amazon Kids and Families director. Parents will have the final say in what the child views.

"[Y]ounger kids still have the freedom to explore the titles that are appropriate for their age group while older kids get to play Monument Valley and see other cool videos, apps, games and books that are just right for them," said Glissmeyer.

The new content which Amazon is introducing includes games and apps like Temple Run: OZ, American Girl, Hot Wheels, Barbie and Sonic the Hedgehog. TV shows that tweens can access include Superman the Animated Series, Star Trek and iCarly, as well as videos like The Haunting Hour by R.L. Stein.

Book lovers can immerse themselves in Harry Potter and The Witch of Blackbird Pond.

FreeTime Unlimited subscription is either $2.99 or $4.99, for Prime and non-Prime members, respectively. To access the content one requires a Kindle e-reader or an Amazon Fire tablet. The pricing is on a per-child basis; however, the e-retailer offers a package discount for up to four customized profiles - $6.99 for Prime members or $9.99 for non-Prime members.

The FreeTime Smart Filters is compatible with fourth- and fifth-gen Fire tablets, which includes the Fire Kids variant. The filter is available as an OTA software update, which will be pushed out from April 27.