This book is a slightly-edited collection of lectures the author gave at various institutions across the US, with the goal of giving a brief overview of classical Japanese literature. It is worth noting that his goal is classical literature, not the full range of Japanese writing; however, he generally takes "classical" to mean "before the Meiji Era," that is, the late 1800s, when Japan opened wide to influence from the West, which left an ineradicable mark on its literature, along with most other aspects of society. With the late 1800s as his endpoint (though he occasionally dips into more modern works), Keene really attempts to cover about 1100 years of Japanese literature in less than 130 pages, and he does a remarkably good job of it. (The 1100 year timespan begins with the first Japanese book, the Kojiki, written in 712.)
I must admit that I did not come to this book with a blank slate, since I've taken a brief class in Japanese literature and dabbled in reading it as well. That being said, Keene, in my opinion, does a great job of describing the major, truly classical works, as well as the main trends in later literature.
The work is divided into five chapters: one on aesthetics, two on poetry, one on fiction, and one on theater. The chapter on aesthetics is based on the Tsurezuregusa (Essays in Idleness), written by Kenkō in the 1330s, a work which Keene himself previously translated. This chapter highlights four main characteristics of Japanese aesthetics--suggestion, irregularity, simplicity, and perishability--and illustrates them with quotes from Kenkō, as well as descriptions of Japanese architecture and culture.
The two chapters on poetry do a wonderful job of showing how central poetry is to traditional Japanese culture. Keene traces this poetry from its earliest, explicitly ritual forms down to modern writers who reject classic forms like the haiku. This includes the little-known long forms (choku and renga), the classic five-line stanzas (uta, waka, and tanka), and, most famous of all, the three-line haiku, with quotations of each form, sometimes even in Japanese (with romaji, not kanji or kana). He also discusses the many uses of poetry, as love letters, as parlor games (including a fascinating gambling game based on matching the halves of 13th-century poems), as accompaniments to paintings, as social criticism (a very rare use), and many others.
The chapters on fiction and theater are similar, first describing classic works, then following the trends through the ages. For fiction, that means beginning with the Tale of Genji, the Tales of Ise, and the Tale of the Heike, down through the comic tales of the 16th and 17th centuries, stopping at the modern border, not making it, for instance, to Yukio Mishima, or even Natsume Sōseki. For theater, Keene discusses the major forms and their history: the highly-rarified Noh, the actor-focused (and burlesque-originated) Kabuki, and the complex puppet-acted Bunraku. His description of the different focuses of each type of theater were very enlightening.
In the end, it's hard to say too much about such an introductory work, which one might try to describe as elongated Wikipedia articles sans hyperlinks. Certainly many seeking such information might, nowadays, turn to Wikipedia or the Internet instead of a book, but Keene's is well-written, with a wealth of knowledge and scholarship behind it, well-chosen examples and quotations, and a great skill for explaining each artform as a development--or series of developments--across time. Yes, it is a book meant for beginners, with a lot of information easily found online today; but there is something to be said for reading such an introduction written by a single, knowledgeable scholar, instead of an unknown horde of Internet encyclopedists. For someone interested in gaining a basic overview of Japanese literature, it is certainly recommended, though one wishing to delve deeper into its pleasures should look elsewhere, and, perhaps, learn the language itself.