So "premise" is perhaps the wrong word for what I've found so far in the first 64 pages of the book. In fact, you can pretty much throw out anything to do with argument or debate because Dawkins doesn't present one, at least not this early in his screed. I call it "screed" because so far, that's all I've read: just one hystrionic claim after another.
First, he presents a completely one-sided view of God and religion. You won't find a word about charitable works, about mercy (on the part of God or His followers), or about how theology developed with the aid of philosophy. None of that seems to exist. A case in point is his claim bout the doctrine of the Trinity. He starts by throwing up the word "consubstantial" and debating its meaning:
What on earth could that possibly mean, you are asking? Substance? What 'substance'? What exactly do you mean by 'essence'? 'Very litte' seems to be the only reasonable reply. Yet the controversy split Christendom down the middle for a century, and the Emperor Constantine ordered that all the copies of Arius's book should be burned. Splitting Christendom by splitting hairs—such has ever been the way of theology.
I'm not sure Arius had an actual book to burn, though I'm sure that there were plenty tracts. However, Dawkins acts as if this was the last word about trinitarian theology. He completely skips over the remaining 1600 years of theological development to make the following claim about St. Gregory the Miracle Worker's description of the trinity:
His words convey the characteristically obscurantist flavour of theology, which—unlike science of most other branches of human scholarship—has not moved on in eighteen centuries.
So he mentions the council at which the definition of the Trinity is defined and clarified, then backs up one hundred years to take the description of the saint who was not exposed to the language of the council and claims that the theology had not moved on? Much less to make the claim that it hadn't moved along in 1800 years? He completely jumped over the work of the scholastic theologians (most notably, St. Thomas Aquinas), acknowledging that they had spilled much ink on the subject (not to mention blood), yet there was no development in trinitarian theology all that time.
Oddly, he accuses theologians of intellectual dishonesty and cherry picking (of statements by prominent scientists) while ignoring the substance of theological work. To him, it doesn't merit attention as a discipline of its own; therefore anyone can engage in theological speculation. So much for epistemology. Nevermind that many theologians historically were also philosophers of the highest mark. The best are rigorously logical in their methods (the Holy father being one such example, not to mention the aforementioned St. Thomas).
In one paragraph, he calls readers to pay attention to terminology. In this, intends to point out how believers tend to latch on to the language in which something is stated rather than on the meaning the speaker intended, noting specifically Einstein's comment that "God does not play dice." He even offers what he considers the most apt interpretation of the statement: 'Randomness does not lie at the heart of all things" (p. 18). This from a biologist that believes that all life evolved through a random process without the aid of any intelligence at the outset or anywhere along the path. Perhaps this is just an acknowledgement that the epistemology of physics differs from that of biology. He makes no bones about not ranting theology the same level of respect.
I'm sure he will eventually come to an actual argument. However, in a scant 64 pages, he's already managed to do poison the well, resort to argument by authority, and cherrypick his own bit of evidence.
So far, not impressed. I'll let you know what I think in 310 pages.