Amazon's Kindle Fire HDX and new Kindle Fire HD tablets are getting an operating system update, which improves some of the nuts and bolts, as well as adding an important feature for using the HDX with your TV.

Several different features have been added to Amazon's custom version of Android, called "Fire OS" in the Fire OS 3.1 update. The update is free, and available for over-the-air download over the "coming weeks," according to the Seattle-based company. If the update hasn't come to your 2013 Kindle Fire HD or Kindle Fire HDX, you can find it for immediate download here.

"The response to our new family of Kindle Fire tablets has been fantastic, and we're excited to add new features we think our customers will love," said Amazon Kindle's vice president, Peter Larsen. "This free, over-the-air Fire OS update brings new features like Goodreads integration, Second Screen, Cloud Collections, enterprise support, wireless printing, and more."

The Fire OS 3.1 update brings deeper integration with Amazon's Goodreads, which the company also brought to the Kindle Paperwhite in an update on Tuesday. Goodreads, which Amazon touts as the "world's largest community of book lovers" with more than 20 million members, was acquired by Amazon earlier this year. It allows to receive lists of recommended books, share annotations they make on their ebooks, and have discussions about what they're reading with other users.

Amazon also has opened up Fire OS 3.1 for enterprise and specifically BYOD support: the new Kindle Fire HD or HDX gets support for some back-end essentials like native Simple Certificate Exchange Protocol functionality, VPN client access, Kerberos authentication, and management support for corporate IT departments. What this means for consumers is that you'll be much more likely to be able to use a Kindle as a work tablet - accessing corporate apps, documents, and secure WiFi networks - without compatibility headaches.

Finally, the last big feature the new Kindle Fire HD and Kindle Fire HDX are getting is a feature they sorely lacked at launch, which is the ability to use the Kindle with an HDTV. The Kindle Fire HDX, for all of its improvements in screen resolution, processor, and other specs, dropped the HDMI port that older Kindle Fire HD had.

Amazon has replaced the HDMI with something much more modern - though with limited compatibility at present. Called "Second Screen," Amazon's Fire OS app promises to "fling TV shows and movies from your tablet to your big-screen TV."

At first blush, Second Screen seems a lot like Google's Chromecast, which allows you to turn a tablet into a remote control for streaming content directly to your TV, while also being able to use the tablet for other tasks, like browsing or email, at the same time.

However, the Chromecast is a dongle users plug into an HDMI port, while Amazon's version relies on third party hardware, and the list is currently disappointingly short: Second Screen only currently works with the PlayStation3, Samsung TVs, and the PlayStation 4 starting "later this year."

A few other minor features have been added in the update, including voice dictation "available in all languages when online," 1-Tap archive, which stores media in Amazon's Cloud to free up physical storage space, and wireless printing. There are also new accessibility improvements for the visually impaired and dozens of other new little features.

According to Amazon's release, the Fire OS 3.1 also includes battery life and performance improvements, plus some bug fixes.