Wonderful and concise introduction into the Five Mountain system of Japanese Rinzai Zen. It gives you context to the Chinese monastic system of the time and is about the best book on the topic in terms of Japanese Rinzai Zen and the medieval monastic system. I took one star off because the structure is a bit weird at times, and it's hard to find a good spot where it explains in short terms how the whole system works (though I'll concede that is not easy to do), as well as the lack of characters in the main text (there is, however, a glossary in the back). Wade Giles has never been my friend, but the book is from 1981 so there's that... Otherwise a superb book.