From Amazon website:
Experience Immersion Reading
"With Immersion Reading, Kindle Fire HD can now synchronize Kindle text with companion Audible audiobooks with real-time highlighting to create a more immersive reading experience, as well as deepen learning and comprehension. Almost 15,000 Kindle books and 15,000 companion Audible audiobooks across a wide array of genres are available."
It's pretty cool, it's text-to-speech only with professional narration.