It would not be appropriate to expect any significant research contribution from a book of this type. Indeed, this book does not try to explore unknown or unclarified materials. Likewise, it does not provide innovative interpretations or a critical assessment of earlier research. Notes are generally absent. The bibliography is almost entirely restricted to works in the English language.
Textual references are usually to English translations or anthologies.
Considering the purpose and the intended readership of the book, this approach seems to be basically acceptable. The book ought to be judged by its pedagogic qualities. And in this respect, we may say that the materials are presented in a clear and intelligent fashion. Nonetheless, and with all due regard to the introductory nature and the pedagogical objectives of the book, a few questions suggest themselves. There is an occasional tendency to present certain opinions and speculative hypotheses as established facts, and to generalize in a somewhat careless manner.