Best books on religion?

[Belacqua]

Today, we don't need religions anymore because we could find out that there are laws that control these phenomena, and that's why educated people are more likely to become atheists.

I'm sure you're right that in the past, at least some religious ideas were explanations for the natural world. These have certainly been superseded by science. 
Are you sure this is or has been the primary goal of religions? For example, science can help us determine the means toward a moral goal, but can't determine what that goal is. The old is/ought thing. 

If only people understood "holy" books literally, we would get rid of religions very soon. 

Maybe so... But are you sure that those books were ever meant to be read literally? I mean, some parts are clearly poetic. They were written poetically, as puzzles or challenges. Ancient people didn't have our science, but they weren't stupid. In fact, they were probably more comfortable than we are with myth and other non-literal expression. 

I think that one of the main reasons that religions will remain for years before their followers realize that they were and are just wasting their time praying and reading primitive-sense books is because some religions' texts are understood metaphorically. Understanding a text metaphorically means that the meaning would change to whatever they want it to be just to seem consistent with today's cultures. 

This seems to me to be begging the question. First, it assumes that they are all wasting their time by reading "primitive-sense" books. How do we demonstrate that a modern person's reading of, say, Ezekiel's vision of the Merkabah, is a waste of time for that person? 

And you seem to think that understanding a text metaphorically, so that the meaning can change, is necessarily a bad thing. Again, begging the question that every text is supposed to have one and only one science-compatible meaning, and that if the meaning is not finally knowable it's a waste of time. 

One of the great things about "primitive-sense" books is exactly that they have been around a long time and the interpretations have changed. At the moment, the Book of Job is not only the Book of Job. It is impossible for us to read it in the way that its earliest readers did. For you and me, the Book of Job is the text of the Book of Job plus all the myriad interpretations that have been made of it over the millennia. It almost doesn't matter what the original author[s] meant to say. It's more important, and infinitely fascinating, to read the story through the eyes of its greatest interpreters, like, e.g. William Blake. 

Or, if you don't like the Bible, there are the Greek myths. Whatever Homer meant originally in the Odyssey, for us the meaning is infinitely enriched by the later Neoplatonic readings, the many operas, adaptations, and responses that we have available. 

For my list of important books, nothing surprising:

Plato; Symposium
Augustine; Confessions
Dante;  Divine Comedy
Blake;  Jerusalem
Nietzsche; The Birth of Tragedy
Buber; I and Thou

and commentary about religion, not religion itself: 

C.S. Lewis; The Discarded Image (Lewis is great as a medieval scholar, not great as a preacher)
Lovejoy; The Great Chain of Being