Like all the recent Google app updates, this is also an ultra-slow staged roll-out, so you will have to wait for hours (may be even days) for the update to appear in your device Play Store.
First talking about the US-centric changes, Google Now will now show information about TV shows you are watching on your internet connected TV as long as both your Android device and TV are on the same Wi-Fi network. Google Now will also alert you about offers whenever you are nearly a redemption location.
Among other changes, there is a new voice action that allows users to play music from Android phones or Play Store. Search app will also show voice actions tips after the update.