I mentioned earlier of Vic Stenger's rather provocative book. I have not read it yet, so I can't make any opinion of it. However, there is a very interesting review of it at PhysicsWeb that you might be interested in reading. I don't think I'm surprised by it, and my original impression of what was done in the book appears to be correct - that Stenger was trying to debunk the "scientific evidence" for the existence of God.
However, as the reviewer has mentioned, at some point, there really is no "falsifying" evidence to disprove such existence. And I do agree with the notion that you can't prove or disprove something like this that is vaguely defined and not falsifiable. One can't disprove something that isn't science.