[NyteSky]

I think it would be extremely difficult to become so escapist one would have trouble with reality. I read a lot when I'm depressed or just sick of it all, and it helps. I've gotten about as escapist as is possible at times but could still function in reality. Too much of anything causes problems, but with books (good ones at least) it's very hard to go too far.
I think everyone needs to escape from reality from time to time, if only to see life from the outside. After all, is having your car break down truly that important? At least you're not being pursued by Ringwraiths! Puts everything in perspective.
It also makes for a good vacation. And like someone said (too lazy to read up and find out who) you can learn a lot. Tolkien's works have all these benefits, and many more. Tolkien is truly the Master of Escapism, among other things.