This book uses two basic themes to enhance reader 1) the search for an understanding of religious life as an ongoing process and 2) the need for recognizing of a variety of ultimate realities when studying religious pluralism.
Streng's book is interesting, though the emphasis on "ultimate transformation" as a tone of religion seems excessively bland. What constitutes an "ultimate transformation" is illustrated, partially, but it seems that the term could be used to rationalize any substantial change in disposition. It also refers to what William James refers to as the actual class of "religious people," who are "exceptional and eccentric" (Religion and Neurology).
The sociological aspects that Streng deals with are really interesting, especially in the context of the personal. But Streng seems to dismiss them when he has the opportunity to explore the connection between the two of them in a way that most aren't prepared to. Overall, it's an interesting read, but it's not going to drop with awe anyone who's familiar with the truly substantial works of religious studies that Streng is responding to.