After you have read all the books, and heard all the lectures, you must still judge what is for you. Books and people can merely inspire you. Unless they awaken something within you, nothing worthwhile has been accomplished. But if you must read books, read many books, so that you will contact as many conflicting opinions as possible. In this manner you'll be required to form your own opinions after all.
Truth is the pearl without price.
Nor should spiritual truth be sold, lest the seller be injured spiritually. You lose any spiritual contact the moment you commercialize it. Those who have the truth would not be packaging and selling it, so anyone who is selling it, really does not possess it. We limit ourselves by thinking things can't be done. Many think peace in the world is impossible - many think that inner peace cannot be attained.