This is one of my favorite books. It's the best on Pureland Buddhism. It gives a history of this schools development, a brief description of all the important historical teachers and practitioners, as well as excellent explanations of the three sutras and their doctrines. The copious diagrams clarifying the emphases of the approach of various teachers is the most outstanding characteristic of Hisao Inagaki's work. Also very helpful are the explanations of the more pertinent Vows of Amitabha. After a general familiarization with Pureland Buddhism, this is the book I would recommend most to deepen one's understanding of Shinrans work and that of his predecessors.
In addition there are other excellent books by Inagaki, some of which I own, and all of which I heartily recommend.