Let me start by saying I have used this text as required reading for several classes in Theories of Learning. I feel it is an excellent presentation of the basic concepts and groundwork needed to understand more complex theories and/or higher forms of learning. The physiological tie-ins are not central to the book, and if skipped it would not be detrimental to a complete understanding of the learning theory. My understanding is that this is the reason they are presented in boxed sidebars and not incorporated into the body of the text.
Admittedly the reading can be dense, and difficult to get through, but I feel this is because the subject matter is dense and complicated. One thing I have found with basic learning theory is that it is much like formal logic, with a cursory examination, many people feel it is straightforward and simple. But once one begins to deal with the `meat' of the subject, and attempts to understand the implications, exceptions, strengths and weaknesses of the topic, then the feeling of simplicity quickly disappears. It is at this point that one will find people either love the topic and want to know more, or they are put off and either blame their dislike for the topic on the presentation or the material itself. In case it is not obvious, I am one of the former types, and continue to enjoy the broader implications of learning theory, the rigor of the arguments involved and the breadth of explanatory power I see in this filed.
This leads me to one final point. I feel the author does an excellent job of relating the basic principals he discusses to real life examples. In particular the chapter on language provides an excellent source for class discussion, informed debate and application of the theoretical mechanisms presented in the first half of the book.