If you really want to specify that you "will read books at the library" just put in a time frame like Aurura said. Otherwise, the meaning can just be assumed from context. Japanese does not really have a future tense like English, because it really is not all that necessary.
If you want to say I read books at the library as a form of habit, you can use a different grammar construction.
So think about it in context. Does it matter which you say? Does either sentence really change the meaning? So you are talking to your friend. How will the conversation go? What are you talking about? Throwing context around a sentence like that destroys any ambiguity. I would not dwell on this, I know you want to see the difference because it is something that is important in English, but part of learning Japanese is learning to put your English speaking mind aside and develop a Japanese one.