Editor/ contributor Steven Heine can be forgiven for being very giddy about the variety and quality of the contributions to this book. It is most unusual to find such even quality and interest-value in a collection of essays on such a mysterious, multi-sided, and rarefied subject.
Everything that reviewer Leighton said about the book is exactly right.
What I want to add (for the sake of koan practicers and would-be practicers everywhere) is that virtually every teacher uses koan practice differently. What you get from the book is like a bunch of 'family snapshots' of the hyper-extended family of koans, many different representations, depending on the time and place and circumstances that the writer is addressing in that particular piece. So you can get a lot of appreciation of what koans are (from this book), and how they can work, but how it comes off between you and your koan teacher is strictly an 'ad hoc' affair. The committed zen practicer eventually has to make a choice between koan-style and just-sitting styles of practice. One may want to step back to the balanced evaluations and history in "Traditions of Meditation in Chinese Buddhism" (Studies in Easian Buddhism, No 4) by Peter Gregory(Editor) to help decide that matter. Whatever you do, don't get distracted by any ratty arguments about "Sudden versus Gradual".
This is now THE best overall book available in English ABOUT the koan tradition, finally supplanting Miura Roshi and Ruth Fuller Sasaki's The Zen Koan, (formerly Zen Dust) after more than three decades. The contributors to The Koan are among the best current American and Japanese scholars in the field, such as Griffith Foulk, John McRae, Ishii Shudo, and Dale Wright, and the material included covers a range of periods and methodologies involving koans, including information not available before in English, such as in the provocative article on the Japanese Soto kirigami tradition. The book makes accessible current scholarship about the history and development of the koan, for example in the overview in Foulk's article. One of the editors, Steven Heine, has previously published two important books about koans, Dogen and the Koan Tradition, and Shifting Shape, Shaping Text, about the Fox Koan, which greatly expand our awareness of the richness and complexity of the koan tradition. Heine's article in this book goes further to show the role of the supernatural in koans. However, the buyer should be aware that this is NOT an anthology of koans themselves, or a collection of commentaries by spiritual teachers, but rather an academic perspective about the history and methodology of the koan. Major koan anthologies, and their sources in the Collected Records of individual masters, or in Lamp Transmission catalogs, as well as multiple layers of commentaries by ancient masters, are now available in reasonable translations. Also a number of respected current Zen teachers have published practice-oriented commentaries for the consideration of modern Zen students. But this book offers valuable background context in the history and development of the tradition and its methodologies. In a previous, deplorably misguided and totally ignorant amazon review, this book was described as "bad," and irrelevant to the "living tradition." There has been a recent tension and unfortunate lack of communication between Zen scholars and practitioners. Happily, this gap is beginning to heal. Scholars are beginning to openly express appreciation for the value of Zen's spiritual teachings. And practitioners have been gaining a deeper appreciation from academic scholars to inform our practice with the historical context of the koans and the varying practice methodologies. If you are actively engaged in koan practice with a teacher in one of the lineages that sanctions only one single acceptable response to koans, maybe you should check with your teacher before reading this book. But for most practitioners, this book will be extremely valuable in giving context for koan work. Such context is definitely relevant to the "living tradition." A prime example is the final article in this book by Victor Sogen Hori, now a professor at McGill University, but previously a long-time Rinzai monk in Japan. According to highly reliable sources, Hori progressed further in the Japanese Rinzai koan curriculum than has any other Westerner. His article on "Kensho in the Rinzai Zen Curriculum" is highly illuminating, precisely explaining the important role of scholarly study in the Rinzai koan practice tradition itself, and clearly dispelling damaging and mistaken stereotypes about kensho that have been sadly prevalent in the West.