I recently built a new built-in bookcase for our lounge room - my collection was previously in a spare bedroom, with no direct sunlight. Our lounge cops some direct sun, in the afternoon, so we have exterior blinds and interior blinds. I was still concerned, so had tinted UV film applied to the window. Feel MUCH better, now. It's also great for privacy, as you can't see in during the day.
Cost was AU$300, for a window measuring 2.4 x 1.5 metres (8' x 5'). Took the installer about 45 mins.
Lincoln.