Dawkins' book makes a perfectly coherent and informative case that atheism should be taken seriously and religious belief scrutinised more severely.
It identifies that Darwin's theory of evolution by natural selection had a pivotal place in the history of ideas, by describing a mechanism by which all the complexity of life can arise without reference to blind chance (natural selection does not happen by chance, but according to well defined and powerful principles) and without invoking the extraordinarily complex and improbable concept of a designer. It goes a bit far, in my opinion, by trying to extrapolate the same theory of natural selection into the history of ideas. This is not persuasive or interesting as it is too reductionist. But that does not affect the general argument of the book.
The book argues the case that morality not only can but must be (and historically was) arrived at independently of the Bible or other holy texts. By focusing on the colourful nature of some of the Old Testament's most outrageously immoral content, beloved of the more inquisitive schoolchildren in religious schools throughout the world I am sure, he fails to address the evidence that the Bible itself (e.g. in Job) denies that faith / God / religion is moral at all. Dawkins also argues that religion is socially harmful in many ways, especially to children, and these charges merit serious debate. For example, he cites a chilling study by the Israeli psychologist, George Tamarin, that shows Israeli schoolchildren willing to justify genocide in a religious war, based on an account of the battle of Jericho in the book of Joshua (see pages 289ff). It is surely for supporters of religion to deal with the evidence if they feel they can, not for Dawkins to enter into a subtle exercise of bending over backwards to give religion the benefit of the doubt. Not all his arguments can survive unchallenged. For example, he is just plain stupid to enter into a discussion about the relative harmfulness of sexual abuse of children compared with the harm done by religious indoctrination and bigotry; the comparison serves no purpose whatever and his comments are crass. Nevertheless, his arguments are serious and require answers.
My paperback edition has a brief preface in which Dawkins answers some of the criticisms made of his book in its hardback edition. An entire secondary literature ( a review of reviews) could develop to pick out the bones from the arguments of his critics. In broad terms, too many seem to me to evade the arguments in this book, not least by using ad hominem attack against its author, as if that even matters. For example, Dawkins is accused of failing to understand religion properly. If so, a more sophisticated exploration of the history of religion could be preferable to Dawkins' simplistic reliance on evolutionary biology, some of which - when applied to human psychology and behaviour - has the unconvincing ring of "just-so" stories and all of which is speculative. Such an exploration, in my own opinion, would certainly add layers of nuance to this discussion - for example, most Christians since at least Augustine of Hippo have had no interest in the value of logical proofs that God exists; they are always invalid even in theological terms - but this would not, frankly, undermine his arguments in favour of atheism. After all, the arguments that God does not exist (or as Dawkins expresses it, that the God hypothesis does not work in the face of the evidence) are far less irrational than the "proofs" that he does and they are more robust than they are given credit for.
The greatest difficuty I have with his opponents is the delusion that any error or misjudgement in Dawkins' arguments constitutes evidence in favour of religion in all its rich complexity (or agnosticism in all its tiresome evasiveness). That is rubbish. Atheists can argue with each other without having to convert to Islam or Judaism or Christianity or Hinduism if they make a mistake, let alone select between their many subdivisions, or the many alternative religions not listed. Imagine a debate between Gould and Dawkins in which the loser must convert to a religious faith; they cannot both be right but it does not follow that one is duty bound to be born again.
[Geology] raised John Ruskin's consciousness and provoked his memorable heart cry of 1851: 'If only the Geologists would let me alone, I could do very well, but those dreadful hammers! I hear the clink of them at the end of every cadence of the Bible verses.' p143
Many of our human ailments, from lower back pain to hernias, prolapsed uteruses and our susceptibility to sinus infections, result directly from the fact that we now walk upright with a body that was shaped over hundreds of millions of years to walk on all fours. p161
We now have four good Darwinian reasons for individuals to be altruistic, generous or 'moral' towards each other. First, there is the special case of genetic kinship. Second, there is reciprocation; the repayment of favours given and the giving of favours in anticipation of payback. Following on from this, there is third, the Darwinian benefit of acquiring a reputation for generosity and kindness. And fourth,.. there is the particular additional benefit of conspicuous generosity as a way of buying unfakeably authentic advertising. p252
As the Nobel-Prize winning American physicist Steven Weinberg said: 'Religion is an insult to human dignity. Without it, you'd have good people doing good things and evil people doing evil things. But for good people to do evil things, it takes religion.' Blaise Pascal .. said something similar: 'Men never do evil so completely and cheerfully as when they do it from religious conviction.' p283
Fundamentalist religion is hell-bent on ruining the scientific education of countless thousands of innocent, well-meaning, eager young minds. Non-fundamentalist, 'sensible' religion may not be doing that. But it is making the world safe for fundamentalism by teaching children, from their earliest years, that unquestioning faith is a virtue.
More generally (and this applies to Christianity no less than to Islam)... teaching children that unquestioned faith is a virtue primes them - given certain other ingredients that are not hard to come by - to grow up into potentially lethal weapons for future jihads or crusades.... If children were taught to question and think through their beliefs, ...it is a good bet there would be no suicide bombers. Suicide bombers do what they do because they really believe what they were taught in their religious schools: that duty to God exceeds all other priorities and that martyrdom in his service will be rewarded in the gardens of paradise. And they were taught that lesson not necessarily by extremist fanatics but by decent, gentle, mainstream religious instructors who lined them up in their madrasas, sitting in rows, rythmically nodding their innocent little heads up and down while they learned every word of the holy book like demented parrots." p348
"Really" isn't a word we should use with simple confidence. If a neutrino had a brain which had evolved in neutrino-sized ancestors, it would say that rocks "really" do consist mostly of empty space... "Really", for an animal, is whatever its brain needs it to be, in order to aid its survival. And because different species live in such different worlds, there will be a troubling variety of "reallys". p416 [Does "really" have a plural form?]