The problem with saying "it's just a book" is that so are many other texts we do believe in. In school we learnt from science, history and math textbooks and assumed that the people who wrote them knew what they were talking about. Sometimes they were wrong on individual points, or succeeded as their tenets were proven false by subsequent inquiry, but the whole textbook system wasn't rejected as a result of this. Apart from a few experiments in science and cultural/experience-based "common sense" there was little apparent difference between these and sacred texts. I believe textbooks are subject to editorial and peer review, but I don't actually see it happen. Discoveries are usually the result of painstaking research, but I don't see that either. I could be living in The Matrix, or The Trueman Show.
I have to pick and choose what I follow. There isn't time to do all the experiments that have every been carried out, and create a system of math from first principles, and check if all those things that are meant to be good/bad for me really are, and still go to the pub. I operate roughly a simplified version of Falsification. Assume it might be true unless something comes up that strongly suggests it ain't.
I was RC as a child. I turned the other cheek, and actually read the bible quite a few times. At some point I could no longer reconcile the idea of a god who was Omnipotent, Omniscient and Omnibenevolent, yet allowed bad things to happen to good people, and more than that would actually punish good people if they failed to play to his/her/its vanity and worship. The imminent/imminant discussion doesn't resolve the issue for me, nor do any of the protestations that "it's all part of a plan". If the deity is forced to do things a certain way (pain and suffering), to shape people as it wants then it's not omnipotent.
I don't deny that there might be something bigger than us out there. I think its quite likely that there is something more powerful, even if it's just our equivalent of the "great white god" the Aztecs saw in Montezuma. What I don't believe in is the omnibenevolent yet vengeful and vain bearded bloke in the sky. He just doesn't make sense to me.