I read this book for a class held at my local Shambhala Center, and for that context I would give the book one more star. For those who might have to muddle along alone through these traditional (albeit simplified) arguments that "prove" and describe the empty quality of mind/phenomena, I think it might not be the source of merriment and inspiration that it was in the context of our class.
Actually, the question of audience is one of the problems with this book. It's subtitled "A Practitioner's Guide...," but probably most practitioners will look to the book this one is based on, Khenpo Tsultrim Gyamtso Rinpoche's Meditations on the Progressive Stages of Emptiness -- or one of the more scholarly treatments of the topic. Undecided about whether he's writing for practitioners, Karr's voice is simple almost to the point of cute, reminding me at times of A.A. Milne, so it would seem that he is writing for non- or beginning practitioners -- but then he asks the reader to take quite a lot on faith, which is not what I would do if I were presenting this body of logic-based teachings to non/beginning practitioners.
Too often, Karr suggests that if the reader doesn't understand an argument, or is becoming frustrated in her attempts to follow an argument, it's because the reader's tenacious ego is threatened by the notion of emptiness. Couldn't it just be because the argument is poorly presented, unconvincing, or even invalid? Western Buddhists, Karr included, seem afraid to critique traditional Buddhist logic. A valid and persuasive argument does not depend on one's realization -- we can respect our meditation tradition even while meeting these old arguments head on, on their own (logic-based) terms.
Also, Karr allows some comparison of the traditional Indian arguments about the nature of mind to relevant arguments made by historical and contemporary Western philosophers, but not in a very thorough way. I would have liked to have either stayed entirely within the tradition whence came these arguments, or to have had a deeper, more trustworthy comparison of Indian and European takes on the nature of mind. As it is, it seems that he "picks and chooses" to support the particular Buddhist view under consideration.
The strength of this book is Karr's discussion of contemplation practice and the verses he chose from classic works that support the arguments, verses which we are meant to contemplate. Personally, I do take it on faith that through such practice, anyone can realize the truths that the arguments supposedly demonstrate. The arguments themselves are simply not overwhelmingly convincing, so, to my mind, it is a good thing that the dharma does not depend on them.