The question of "believing in God" or being an "atheist" is rather difficult for me.
I would say that I believe in "God," but the way that I define "God" probably makes me more or less an atheist.
Anyway, our beliefs about God say more about ourselves than they do about God.
Text-based religions like Judaism and Christianity have are based on documents, yes -- but these documents are often vague and cryptic and open to numerous interpretations. The Torah or the Gospels are just lifeless books without people -- a community -- to read, study, interpet, and live them. That gap between the text and its application -- the human element in revelation -- gives tremendous power to the individual.
In Judaism, we have the teaching that the Torah is no longer in heaven -- its in our hands to do and to teach (and to interpret it and change it as necessary). Catholic Christians (Roman, Orthodox, and Anglican) have the evolving Sacred Tradition that supplements and explains the Scriptures. Even sola>
We are all in the gutter, but some of us are looking at the stars.
~ Oscar Wilde