There are two keys to that title, because this book depends on very careful use of words. One is 'atheism', of which more in a moment, and the other is 'Christendom'. It's 'after Christendom', not 'after Christianity.' Perry argues that where initially Christianity was considered atheist by the Romans, because it ran counter to the gods of the state - and Perry effectively defines atheism in this way, as denying the gods of your state - with its establishment by Constantine, Christianity became watered down and in that form, as Christendom, provided the state god, so was a worthy target for atheism. However, since the Enlightenment and particularly in a modernist secular society, the Christian god is no longer the god of the state. Instead, Perry suggests, our modernist state gods are Mars and Venus, as represented by everything from military force and shouty domination on the one hand to commerce and greed on the other. (And these are the 'gods' he suggests the New Atheists follow.)
By contrast, Perry suggests, at the heart of Christianity is acceptance of the 'other' - looking outside ourselves rather than inwards, reaching out to the rest of humanity, the universe and its creator (if it has one). And this, he suggests is the real way forward, the only true justification for existence in what otherwise is a short life with little meaning. He suggests that by taking this approach we avoid the errors of deism - suggesting God could exist, but only starting things off before leaving things alone, the god of the gaps - and of theism, where God is constantly interfering, answering random prayers and has to be held to account for all the horrible things in the universe. Perry's God creates the universe in the way it has to be because there is no denying evolution - violent - but is accessible if we begin to truly care for the 'other' - to consider all humanity of equal importance and to live accordingly. It's not, he says, about 'pie in the sky when you die' but about making our world better with this outward looking stance.
Along the way, Perry throws out a lot that will shock many traditional Christians. He suggests that much of the Old Testament, for instance, that makes it clear that God is a nasty, vindictive mass murderer, is a product of a flawed human interpretation by those who wrote it. And I suspect the majority of Christians' beliefs through the centuries will also be considered flawed, influenced as they have been by the strongly theistic picture that has dominated the church for much of its life.
Some of the specifics in the book I have problems with. There is an assumption throughout that this pursuit of 'otherness' is a good thing, and that the modernist individual-centred approach is wrong. I'm not saying I entirely disagree with this, but I never saw any argument to justify this assumption - it is, as far as I can see, a given. If we accept that for a moment, Perry suggests that the Bible, and particularly the New Testament is built on this acceptance of 'the other' - and yet while Judaism may embrace 'the other' in the form of God, it isn't usually considered a religion with such an outward facing approach to other people. Even Jesus demonstrates this: 'The woman came and knelt before him. “Lord, help me!” she said. He replied, “It is not right to take the children’s bread and toss it to the dogs.”' Is that about embracing 'the other'?
Similarly, I struggle with Perry's attitude to science. While I accept that scientists can verge on scientific imperialism as he mentions, and that the really interesting thing about science is not facts but the exploring, I can't really go for the statement that 'science is simply one means of understanding who we are. There are other equally important and no less valid means of experiencing the world.' It's true in a trivial sense - the joy of seeing a sunrise over a beautiful landscape is an 'important and valid means of experiencing the world.' But it isn't comparable to science, it's a totally different thing. And science is uniquely valuable in many ways. Certainly the author gets in a bit of a tangle when he takes on science, telling us that the LHC enables us to produce and trace the paths of quarks (nope), or when he doesn't spot that black holes aren't observed phenomena that challenge general relativity, but rather were predictions of general relativity that may explain observations.
Overall, the book gives the reader a lot to think about. I don't think that it will be of interest to New Atheists, which is a shame, as a lot of what Perry says about the nature of atheism is very insightful, but they would be put off by the amount of the book that is explicitly Christian. (I do wonder if Perry's dismissal of the New Atheist/Western governments' attitude to Islamic terrorism stands up to the atrocities of ISIS.) However, this is a book that all thinking Christians should read (the left wing politics that it's hard to separate from the original version of Christianity might not go down well in some quarters, though). The only danger for them is that, if they accept Perry's view, they may totally change their viewpoint. Is, for instance, going to church more about Christendom than Christianity? (This is something Perry doesn't address explicitly.)
However you look at it, this is a book to challenge the thinking of atheists and Christians alike, and as such is very welcome.
You can find Atheism after Christendom at Amazon.co.uk and Amazon.com