The Via Negativa or "Negative Way" is a way of speaking about God which limits itself to negative statements. The assumption is that we cannot say who God is, only what he is not. Thus, anything we can say about God is more wrong than right. Whatever similarity there may be between something we say and how God is, there is a much greater dissimilarity.
To show why I really hate much of any emphasis on this method of theology, let me point to a test case: God is love. The Bible has a huge number of positive statements about who God is, and only negatively in order to correct misunderstandings. The negative statements are often there to emphasize the positive ones. To follow the Via Negativa I would have to say that, when I say "God is love" I am speaking by analogy, that I mean that the closest I can come to expressing this emotion of God's is to call it love. What then? Are we not to love as he loved? Do not the Scriptures themselves define what we are to understand by this word "love"? I do say that God's love is greater than any mere human love can be, but I most definitely assert that it is of the same sort, but purer, greater, stronger, unflinching. So great that, even while we were yet sinners, he died for us.
This is a God we can know, not merely by the shadows he casts on the world, but by his entrance into the world. Yes he is greater than we are, but we are made in his image. We have, by the Spirit of God, the mind of God, to know God. Is God too weak to be able to communicate himself accurately in human language? Is he unable to lift us up by his Spirit to know him? Indeed, we will know him fully one day, just as we are fully known, but that is not to say that we do not know him now, we are in Christ, we see with his eyes. Whoever has seen the Son has seen the Father, and we who are saved by Christ have been made able to see Christ, the Son.
It may be appropriate to say that what we say may not communicate fully what we mean. We may find ourselves unable to quite articulate what we mean by what we say, but to infer from this that we ought to settle for this in any degree is to give up at some point. Rather, though we admit that we do not always succeed in saying fully who God is, yet we have tools given by God which we ought to therefore use to speak about God as much as possible. It may take a book to articulate to some degree of accuracy one point of one doctrine of some aspect of God, but the length does not mean it is impossible. If saying that God is such-and-such is so inaccurate, then write more, tell me in what ways it is inaccurate, or you have told me nothing useful. How can I worship a God for what I know he is not? That would be only to worship a lack of evil, not a fullness of God.