I remember hearing Brian Mclaren talk a few years ago about an interview he' d given at a conference. I believe it was with Dallas Willard and they were discussing why a trip to your average bookshop would reveal a great upsurge of interest in Buddhism and New Age, but a sharp disinterest with Christianity.
Willard's response was simple and - it seems to me - spot on: "Christianity is a set of doctrines, whilst Buddhism offers a way of life."
Now, this is a platitudinous misrepresentation of Buddhism in its native lands. Anyone who has read much about modern Japanese culture has run across the aphorism that "the Japanese are born Shinto and die Buddhist." Beneath that is a deeper truth: that a buddhist "way of life" is the fartherest thing from their minds. The Japanese are the only modern true pagans left, and religion as westerners tend to see it is just not part of their lives. There is nothing systematic about it; their way of life is Japanese first, and Shinto and Buddhist observances are simply subsidiary parts of that life, put on and off like (and for that matter as) ceremonial clothing.
And it's not at all irrelevant that, in the USA, Buddhism tends to get lumped with "spirituality" while Christianity gets lumped with "religion". The latter word suggests something ritualistic, to be sure; but it also suggests something systematic and even life-encompassing. "Spirituality" suggests dabbling and a lifestyle-accessory attitude.
The thing is that mainline Christianity has already had it out with the "doctrine" matter, mostly to a bad end. It's not really the doctrines of Christianity that are the problem. The papers like to claim that it is, but that's because they need to controversy to have something to cover, and because it makes them look smart when they really don't get religion. The big problem is that Christianity IS all-encompassing and sets out a way of life-- which people don't want to follow! The "solution" in the West was to make all sorts of distinction between Church and State and what-have-you, leading in Europe to the collapse of moral values that was WW II, and in the US to a corrupt bargain between Church and Business which Business gradually reneged on anyway. Throughout this there was always a mainline stream of objection; but since the western wolrd these days seems to be largely made up of rebellious children, the last thing anyone wanted was a church that told them what to do. So this fiction was made up of a "doctrine-only" Christianity, something that never ever existed and doesn't exist now.
It did exist to a degree in American fundagelical Christianity, because there the Church-Business bargain held. And because it held, it led to corruption, personal in the case of various now more-or-less fallen church leaders, but also more systematic. The US is the locus of the "sex is the only form of immorality" Christian ethics, even though mainline liberals had been criticizing business (lack of) ethics for decades.
Now, bookstores are stocked along strange reasons, as might be seen in my previous articles on bible buying. Christian bookstores and book services eat a lot of the Christian book market. But I suspect that, at the local Borders anyway, a lot of the wierdness can be traced to bookstores being heavily staffed by the kind of people who do buy into the spirituality as lifestyle accessory ethos.