Note that museums do display historical documents to the public in showrooms; the very fact that they do this indicates they believe it can be done safely. My study of what museums do indicates that besides encapsulation, minimizing light exposure and making sure you use the right type of light is what's most important. Always use fluorescent lighting instead of incandescent lighting, and make sure it's the lowest wattage you can manage. Keep the lighting off whenever you're not viewing the books, and keep ALL natural sunlight out of your display room. Eliminating ambient light is VERY difficult--I've never been able to sufficiently achieve it in a den or office or other similar spare room, nor have I ever met anyone who did. If anyone here has found a great way to eliminate window sunlight, please share your secrets.
We picked up some custom cut shades from, I believe the local Home Depot, that were called blackout shades. I have them in the man cave and they block out almost every bit of light. (And I keep my comics/statues/and a bunch of screen used costumes in that room, so it has to be well protected) They are the horizontal accordian type (for lack of a better description) and are pulled up and down by the bottom of the shade, there are no strings or any other devices. Might be worth checking out.
What was your motivation for installing them? This appears to be one here: That does look like it. Motivation was entirely for the protection of our collectibles. And these sounded like they fit the bill. And they do seem to work just as advertised.