Paul Heelas & Linda Woodhead, The Spiritual Revolution: Why Religion is Giving Way to Spirituality (Blackwell, 2005).
This is a very interesting book, written by scholars of religion, on the topic of whether traditional religion is giving way to those who consider themselves "spiritual but not religious" (known as SBNRs in the literature). SBNRs, often associated with the New Age movement, might associate with a stunningly wide-variety of practices and beliefs: yoga, crystal magic, homeopathy, tarot, holistic medicine, and more. As Heelas & Woodhead note, "Even a cursory glance around the local bookshop or a stroll around the shopping centre leaves little doubt that Christianity has a new competitor in 'the spiritual marketplace'" (p. 1)
Helpfully, Heelas & Woodhead fit the rise of SBNRs into a broader social context: that of the rise of subjectivism in general. Subjectivism is a turn towards individualism, and "has to do with states of mind, memories, emotions, passions, sensations, bodily experiences, dreams, feelings, inner conscience, and sentiments" (p. 4). The rise of subjectivism can be noted in everything from self-help books to motivational speakers and more, and has a key element that "[t]he subjectivities of each individual become a, if not the, unique source of significance, meaning and authority". (p. 4) The authors contrast this "subjective-life" with "life-as" culture, which emphasizes external authority, hierarchy, and role-recognition. Traditional religion is strongly related to "life-as" culture, whilst the new move towards spirituality is strongly related to "subjective-life" culture.
In order to gauge the relative strength and future trends of traditional religion versus the new spirituality, Heelas & Woodhead study what they call the "congregational domain" (traditional religion) versus the "holistic milieu" (SBNRs) in a single small English town (Kendal) of about 27,000 people. Through an extensive, multiyear project, the authors and their team of researchers gauged the extent of activities taking place in the congregational domain and the holistic milieu. They reached some very interesting conclusions. First, and contrary to my own perception, they found very little overlap between participants in the two areas: only 4% of participants in the congregational domain also participated in the holistic milieu (p. 31-32), and only 16% of persons active in the holistic milieu were regular churchgoers (p. 48 n.10). I found this surprising based on other material I've read which argues that a "cafeteria" spirituality is common, where many people, including regular churchgoers, have picked from the menu of New Age beliefs. "In Kendal at least, such a post-modern condition is scarcely in evidence. Instead, the congregational domain and holistic milieu constitute two largely separate and distinct worlds." (p. 32) Second, the authors were able to assess the regular strength of each area: they found that participants in the congregational domain outnumbered those in the holistic milieu by about 5-1. No overwhelming "spiritual revolution" has taken place yet. Third, however, they found that trends clearly favour the holistic milieu--not only has there been a dramatic rise in the area in just the past few decades, but there has been a slow but gradual decline in the congregational domain. Further, the holistic milieu has gained extensive visibility in general culture, as seen by books, classes at gyms, newspaper columns, etc. It's quite conceivable that in just a few decades, participants in the holistic milieu will exceed those in the congregational domain.
There's a lot of other good material in the book, and I highly recommend it. The law review article I'm working on now is about what the rise of the "holistic milieu" means for our understanding of religious freedom.