From the author's post announcing the book:

Eight Million Ways to Happiness is the culmination of more than a decade of research, exploration, and living. It is a story of re-connection, as I traveled Japan to explore my nation's patchwork of spiritual traditions after the loss of my mother, and later my father. It's a cultural history of the Japanese spiritual landscape, and also something more: a roadmap for those questing for meaning in the modern world, but who shy away from locking themselves into any specific faith.

The book's title comes from the Japanese idiom yaoyorozu no kami, literally "eight million kami," kami being what we call spiritual beings in Japan. Once, we saw them in everything: the heavens above, the ground below, the trees, the rocks, the rivers, the seas, the tools we used, even the words we speak. To us, eight million isn't a strict accounting. It is an awed description of an uncountable multitude of incredible diversity, of a spiritual space defined by incorporation rather than rejection.