Spoke to a prof from University of Hawaii. Requested an introductory list on Eastern philosophy. Was pointed to this very clearly-written book for Shinto.
Found the book unexpectedly interesting -- in particular its first chapter, on Shinto spirituality: fertile food-for-thought for philosophy of religion (eg, definitions of "religion" and "spirituality", and nature of religious experience), as well as novel take on mental dualism.
The remainder of the book: essentially a survey of the history of Shinto -- less interesting philosophically, but still engaging as a case study of religious development. I do feel, on having read the book, that I've travelled miles in my understanding of Japan.
What does Kasulis say? He distinguishes "existentialist" from "essentialist". In "Mary is a comedian", the description is "existentialist" if you're describing (ie, Mary tells a lot of jokes) but "essentialist" if you're commenting on Mary's nature (ie, Mary tells a lot of jokes *because* she is a comedian). Kasulis wants (if I'm reading him properly) to "rescue" Shinto -- to separate an existentialist Shinto heart from an essentialist and expansionist ideology.
The middle section covers some 1400 years of Shinto development, along with forays into Japanese history generally. It's fascinating, but biased towards the existentialist yay, essentialist boo position. And there are worries here. On the one hand, maybe you're won't find a summary this short, and this comprehensive, without this level of vagueness; on the other hand, the glossing-over, and neatness of explanation, might raise the suspicion of skewed narrative. I just don't know enough Japanese history to fairly judge.
Here's my own glossed-over summary of some key points:
Chapter 1: When people disconnect from capacity for awe, they feel homeless. Shinto spirituality is about learning to feel "at home" with spiritually encountering mystery -- and not trying to explain away such experiences. Awe can come upon you suddenly, or can be found in the everyday; can be caused by nature (a glorious sunset), or by the manufactured (the original Magna Carta); and can be associated with joy or fear. Such presences are "kami". Kami is interdependent with the material, not separate from it. Shinto marks places that are specially able to give rise to feelings of being part of and "holographically" reflecting the whole. But one requires a "mindful heart": Shinto practices nurture sensitivity and responsiveness. Kasulis also discusses whether Shinto counts as a "religion" or is a cluster of folk beliefs.
Chapter 2: Shinto themes (including naturalness, simplicity, purity and taboo, purification, and separateness and communal solidarity) are part of the warp and woof of everyday Japanese life.
Chapter 3: Time immemorial up to eighth century. Native religion was in part animist, but "kami" was also associated with forces of nature. Shinto myths lack a cosmic struggle between good and evil. Kasulis contrasts two key eighth-century collections of folk traditions ("Nihonshoki" and "Kojiki") and touches on connections of the former with justifications for empire.
Chapter 4: Eighth to nineteenth centuries. Growth of essentialist Shinto was contravened by Buddhist-Shinto syncretism. When Buddhism waned, Shinto attempted to build an original philosophy -- the "Native studies" movement, exemplified by Motoori Norinaga, who spent three decades interpreting Kojiki.
Chapter 5: 1801-2002. Hirata Atsutane rendered Shinto suitable for expansionism, by, inter alia, emphasizing the emperor as holographic entry point and introducing afterlife reward. Starting with Hirata Shinto, the government supported an essentialist ideology of "State Shinto", which involved, for instance, distancing Shinto from Buddhism, and a religion of "Shrine Shinto", whose practices were compulsory and whose beliefs were equated with being Japanese. The allied powers could not dismantle State Shinto entirely: Kasulis discusses the Yasukuni shrine.
Chapter 6: It's difficult to separate "existentialist" and "essentialist" in Japan. Also, the existential/essential distinction can be applied to many, if not most, religions, and there's frequently a power struggle in terms of the dominance of one or the other.