Buddhism is one of the major religions in Japan, but it is not the Buddhism one thinks of in India, or that commonly comes to mind in the West. The Japanese religious tradition tends towards Mahayana Buddhism, rather than Theravada. Mahayana, especially in its Japanese forms, such as in Shin Buddhism (Pure Land Sect), actually has remarkable parallels to Christianity, with notions such as hell, an afterlife in a paradise-like realm, sin and salvation. Andreasen concentrates on this sect of Shin Buddhism, rather than Zen Buddhism or Theravada. In this book, Andreasen's treatment of Japanese Buddhism is rather light. He does not delve into the details and complexities of his subject, nor does he attempt analysis. However, what he has done very well in this book is bring together a large number of documents which are very enlightening (sorry) for the reader and eminently readable. Andreasen's own writing is easy to understand and clear, if not deep.
For the collection of documents, it is a book worth looking into. But for a much more detailed and exhaustive look at Mahayana Buddhism, I would recommend looking at Paul Williams book 'Mahayana Buddhism: The Doctrinal Foundations'.