Mounce's "Graded Reader" is intended as a transitionary textbook for students who are in their second year of Greek. I give it three stars because, while it is better than any alternative I have found, I think it is lacking in several respects and is somewhat disappointing given the quality of Mounce's BBG.
The book consists of 20 extended passages in Koine Greek, coming primarily from the New Testament. The readings cover all four Gospels, several letters, and Revelation. In addition, a Septuagint Psalm is thrown in, as well as an excerpt from the Didache, one of the earliest teaching documents of the Church. In addition to the passages, there is an introductory section on a technique, developed by Mounce, called "phrasing." It is essentially a means of diagramming Greek sentences to clarify the relationships of the parts of the sentence. Also, the book has a synopsis of Wallace's extensive "Greek Grammar Beyond the Basics," and a "cheat sheet" which lists the various cases, tenses, etc., and their uses.
The passages themselves have footnotes, which are primarily used for vocabulary. The footnotes gloss words that occur 20 or fewer times, and in addition to a definition provide the number of occurrences of the word in the NT. This is useful for finding the words in Mounce's flash card deck, if you have that. Aside from the vocab notes, each page explains various theological and/or grammatical concepts. At the end of each passage is a grammar summary and reflections on the text. I agree with a previous reviewer that Mounce's theology can be ignored.
My biggest complaint about this book is that the commentary in the notes is not very useful. The footnotes consist primarily of references to other author's commentaries. They tend to be in this form: "Why did Paul use the aorist here? See John Doe, p. 100." This is not terribly helpful, since he references 15 or 20 books, few of which I have. If Mounce is simply going to refer to someone else's commentary, why not just buy the commentary and skip Mounce's book? Since 90% of his notes are question format (e.g., p.7 "What is the antecedent of auto?") without answer, they do serve to call attention to important concepts, but if you can't answer his question you are out of luck.
That Mounce is the master of morphology is certain. However, one can see from his BBG that he is light on syntax, and I found many challenging concepts unmarked even by one of his questioning footnotes. After struggling through Ch. 7 (Romans) with extreme frustration, I recalled that at the beginning of the chapter he said the grammar was not difficult. If Mounce is in tune with students' morphological struggles he is not in tune with their syntactical struggles. Nonetheless this book is more useful than a non-commented text, and better than the JACT New Testament reader. Still, one hopes that a better reader with commentary will show up some day.