Get it here
My general rule with understanding hard subjects, like philosophy (hard for me!), is to read the original source matter. I used to read books about, say, Plato, and got nowhere. Then I read Plato himself, and it all seemed rather straightforward. There is a reason that the original works have survived, and that commentaries are replaced every few years.
The reason I mention this, is that I tried this approach with the Tao, and it did not work. A proper understanding of the Tao was denied me by reading the Tao Teh King. So I hoped the Book of Tea would help me to with it. This failed too. I have ignored my other general rule of understanding hard things: take a long time.
Still, the Book of Tea has much more to offer. On one level it is a history of tea drinking in the East. But, more thoroughly, it is a silent attack on westerners who had too little respect for the traditions of Japan, and the East in general. The author is very anxious to present Japanese culture as the equal or superior to its western counterparts. The book lays bare the centuries of tradition that underpin the seemingly mundane activity of drinking tea, and draws parallels between this and the appreciation of art generally, with reference to Zen and Tao philosophy.
Between the lines I got a strong feeling that the author felt himself to be under siege from a foreign culture, and was fighting a losing battle to persuade his own people to preserve their own culture. So the book probably still has lessons to teach the west, and not all about tea.