The book has an introduction, not by one of the authors above, then begins with what I guess could be called an essay by Vattimo, called "Toward a Nonreligious Christianity".
One thing I want to say is that the essay is written in an accessible way. Not that it is all of that easy to understand, and I can't claim perfect understanding of it all, but I'll take the chance that I do understand him to some degree.
Vattimo seems to claim so kind of Christian belief, but it also seems to be of a peculiar sort. For example, on p. 42, in regards to the Lord's prayer, he says
...I know preciese that the words I am using are not intended to convey some literal truth. I pray these words more for the love of a tradition than I do for the love of some mythic reality.
and here, on p. 38
Likewise, with the language of the gospel, I can only understand it as that which is not ontic, not given in the external world, not is it meant to be interpreted realistically.
Given such statements, then, I don't think it's unrealistic sees the Bible as largely mythic, not history; as mostly a collection of stories, whether divinely inspired or not I'm uncertain as of yet. In fact, I'm pretty well convince, reading other things he's said and written, that he doesn't believe in God at all.
There are two things I want to focus on from this essay. The first is in regards to truth. From p. 37
In Christianity there is a fundamental commitment to freedom. And, to add a bit of scandal, by standing for freedom, this includes freedom from (the idea of) truth. After all, if there really is an objective truth, there will always be someone who is more in possession of it than I and thereby authorized to impose its law obligation on me.
And further down that page.
...if Christianity did not liberate us from objective truth, how could we even maintain our belief in Scripture, or how could we prevent Scripture from being logically inconsistent, if not utterly absurd?
There are several lines this ideas of the Bible being illogical and absurd could have taken. For example, "historical Jesus" which seeks to de-mythologize Him, meaning that it begins with the assumption that accounts of His miracles and His claims to divinity are untrue. There have also been question about the historical reliability of other parts of the Bible, particularly in regards to the early part of Genesis. I think this is partially was on his mind, at least by some things he said in other parts of the essay.
And so we have one of the fruit being born from the compromise with evolution--Scripture when taken as truth becomes "logically inconsistent, if not utterly absurd". What is left? from p. 41
In this sense, emancipation actually consists in pursuing secularization, which is to say, emancipation relies on the process of desacralization, in having a better understanding of the spiritual sense of Scriptures by reading them spiritually.
Which leads us in the direction of the other thing I want focus on. From p. 44
As I see it, Christianity is moving in a direction that cannot but lighten adn weaken its moral load in favor of its pracrical-moral charity. And not only the weakening of its moral-metaphysical assumptions, but, by this transformation, charity will eventually replace truth.
I cannot say how familiar that sounds, how much what he says seems like things others are saying. There does seem to be a movement to treat the record of Jesus' life in the Bible as some kind of myth, while also wanting to treat them to some extent seriously. It really does seem as if their object of faith is not so much Christ, not even so much the stories about him, but their ideas and the 'truths' they claim to glean from them.
And as a consequence, what is left? We have some people who try to make concepts of Heaven and Hell being real places where we go when we die into a form of what they say is some kind of unbiblical dualism. They try to downplay the role of beliefs and creeds, and emphasize their forms of social and charitable works. Charity replaces truth, a Vattimo says.
I do not think that I need to defend the importance of charity or love in Christianity, but I do see the need to defend the importance of belief in Christianity now. To more-or-less quote C.S. Lewis from "The Four Loves", "Love, having become a god, becomes a demon". Not even charity can take the place rightfully belonging to God without become an evil thing. One can see that welfare systems which allow those meant to be helped to live lives of sloth, and which make the people dependent on an organization or a government to provide for them. One can see it as well in socialistic ideas such as taking from those who have, irregardless of whether they gained rightly or wrongly, and giving to those who have not, again irregardless of whether they can manage their gains or not.
After all, does the Bible also not say "If a man will not work, he shall not eat"? Didn't Paul tell some in Thessalonica to stop living idle lives and start doing something productive? Charity is good, but it is not God.
Vattimo seems to be saying that charity is somehow the main thing. But in making the Bible nothing more then a book of nice stories, he undercuts his own position. Because if the Bible is only a book of nice stories, if its morals are now of no importance, then by definition even the commands to charity are only human constructs, and his holding them over some other ethic--for example, one which says charity is an evil which must be done away with--becomes in the end only his own preference. If there is no divine command behind it, then there is no compulsion to live by it. If there is no objective truth, then not even charity can be something we must pursue. Vattimo's "message of charity" becomes only a message, not something we must follow, not a command, only a preference, which people can (and no doubt will) discard or use as they see fit.
What you will find behind the "death of God" and the "Scriptures as mythology" rhetoric is simply a 'god' who is made in the image of people like Vattimo. Vattimo is openly gay and a socialist, and it would not be surprising if his 'god' and his 'mythologized bible' wind up agreeing with his economics and politics, and also doesn't look with disapproval on his sexual activities.