The Book of Tea by Kakuzō Okakura.  
The Book of Tea was written by Okakura Kakuzo in the early 20th century. It was first published in 1906, and has since been republished many times. - In the book, Kakuzo introduces the term Teaism and how Tea has affected nearly every aspect of Japanese culture, thought, and life. The book is noted to be accessible to Western audiences because though Kakuzo was born and raised Japanese, he was trained from a young age to speak English; and would speak it all his life, becoming proficient at communicating his thoughts in the Western Mind. In his book he elucidates such topics as Zen and Taoism, but also the secular aspects of Tea and Japanese life. The book emphasizes how Teaism taught the Japanese many things; most importantly, simplicity. Kakuzo argues that this tea-induced simplicity affected art and architecture, and he was a long-time student of the visual arts. He ends the book with a chapter on Tea Masters, and spends some time talking about Sen no Rikyu and his contribution to the Japanese Tea Ceremony.