Atheism Explained: From Folly to Philosophy (Ideas Explained)
A popular theme of atheist propaganda is that the person being addressed (usually a Christian) doesn't believe in Zeus or Allah, so it is only taking it one step further to disbelieve in the Christian God. I grant that something similar to this may sometimes be useful as a rhetorical goad to get people to look at the fleeting nature of all ideologies, including theistic ones, and mentally to step outside of their own cultural milieu. But it doesn't cut very deep. Christians, of course, do believe in Allah, which is simply the Arabic word for 'God' (Arabic-speaking Christians call God 'Allah'-what else?). God, Allah, and Yahweh are just different labels for the same hypothetical entity.
Even Zeus could be defended as another label for God, by claiming that he is more powerful than the Greeks supposed. It was presumably this train of thought which led Kierkegaard to say that a man who worships an idol in the right spirit may be worshipping God. But can the Christian God really be the same as the Jewish and Muslim God, if he is 'three persons in one'? Yes, just as many people can agree on the existence of some historical personage, while only some of them adhere to the theory that this personage was a case of multiple personality disorder.