Living With a Wild God: A Non-believer's Search for the Truth About Everything by Barbara Ehrenreich, book review Atheists: The Origin of the Species by Nick Spencer, book review

I once met a woman who saw the Virgin Mary. I was in the Irish pub in the Marian shrine town of Medjugorje in Bosnia when a woman from Dublin told me that, on a visit to the town four years previously, she had seen the mother of Christ.

She'd been having a quiet fag behind the shrine church of St Jacob, bunking off mass, when an enormous, instantly recognisable Mary reared up in front of her. She couldn't have imagined it, she said, because a Spanish women standing close behind had shrieked: "Madre de Dios!" and had thrown herself on the ground.

I wasn't that interested in what she had seen, or thought she'd seen, for some reason, which is why I never asked whether Mary had appeared in regulation blue, or some other colour, for example. What I wanted to know was what the woman from Dublin had felt; it wasn't the vision itself but the impact of a vision on a visionary that intrigued me. I half-expected to hear that she'd felt "magnified", or some other biblical-sounding phrase, and felt disconcerted when she said her main feeling had been one of embarrassment.

It was because she had been quite content with her workaday Catholicism-lite, whose only real obligation was to go to church occasionally and take disabled kids from Dublin on holiday, which is why she'd gone to Medjugorje in the first place. Now she felt singled out and observed – put on the spot. Her life had been sliced into two halves, pre and post-vision, and it neither could nor would be the same again.

Her story came to mind when I read Barbara Ehrenreich's account of her own mystical experiences because if even a believer can find a vision embarrassing, you can only imagine the double embarrassment it might cause a dyed-in-the-wool atheist. Ehrenreich had form in this department because she wasn't some shoulder-shrugging sceptic. She hails from a long line of militant atheists that dates back to a fiercely free-thinking great-grandmother who screamed blue murder when a priest tried to read her the last rites, and hurled away the crucifix he had placed on her deathbed.

From great-grandma down, atheist begat atheist and atheist married atheist, spawning a mutually supportive clan of God-deniers, leading all the way to Ehrenreich's parents, who ended up cordially loathing each other but still had their atheism in common. No wonder Ehrenreich felt acutely embarrassed, ashamed even, when she had series of ecstatic mystical visions in her late teens – and dealt with it by burying all memory of it, having concluded that she must have been mentally ill. For decades she busied herself in feminism, social activism and raising children. It was only when the children grew up and a hurricane blew away her home that, while salvaging remains from the ruins, she chanced on her teenage diary in which she had recorded these strange events and felt compelled to re-examine what had happened to her back in 1959.

Of course, what Ehrenreich experienced was nothing as straightforward as a vision of the Virgin Mary. Indeed, precisely what she did see is hard to work out, which isn't surprising, as language relies on the tools that the surrounding society provides it, and for us English-speakers, the framework comes from the Judeo-Christian religious experience. So, when Ehrenreich talks of mystical epiphanies, she has no option but to borrow from the lexicon of the faith that her redoubtable great-grandmother rejected.

She is not exactly a repentant atheist, even now, as she sees an important distinction between her visions and those of St Paul, say, mainly because they were not accompanied by any kind of message. As she puts it, "My own 'epiphanies,' to over-glorify them, had nothing to do with right or wrong, good or evil, kindness or cruelty. Paul's blinding vision on the road to Damascus had come with instructions – stop persecuting Christians and start preaching the faith. My vision, if you could call it that, did not. Whatever I had seen was what it was, with no moral valence or reference to human concerns."

She still does not "believe", therefore, and certainly not in the big-daddy God of the Christians – "that great mashup of human yearnings and projections". She belongs in a third zone, not god-filled, not god-less, but no longer willing to deny the reality of her experience, and reluctantly persuaded that, whether or not some kind of "Other" is out there, it's worth exploring.

Ehrenreich's account, which is compelling as well as instructive – not least because of the gory details about her parents – is a reminder that putting people into neat categories, marked "atheist", "agnostic" and "believer", has only limited use as a guide to people's actual beliefs, or lack of them.

Nick Spencer, meanwhile, provides a potted history of the tradition that Ehrenreich – at least to a degree – has distanced herself from. From the Ancient Greeks to Marx, Freud, Richard Dawkins and the American Madalyn O'Hair, here they all are, in a kind of procession.

The title of this book is somewhat misleading, as it's not really about the origins of atheism but how one irreverent thought led to another across a span of roughly two millennia. One problem with this book is that, apart from O'Hair, who weirdly ended up being kidnapped and killed by a fellow atheist campaigner, it's a tale of rebellious white men versus the Christian Church. Why the Arab-Muslim world is so resistant to the argument for atheism – why the apparent contradiction between science and revelation does not seem to bother them – is not explained. India is also left out of the picture. If religious faith and its opposite do not feed off each other in the same parasitic fashion that they have done for centuries in the West, it would be interesting to know why.

Marcus Tanner's latest book, 'Albania's Mountain Queen, Edith Durham and the Balkans', is published by I. B. Tauris in June