In this post I will try to address some of these issues using an FAQ format. For starters, I will throw out my own ideas (based on my experiences, opinions, and prejudices) and hope that others will throw out their own ideas. Hopefully, we can get a meaningful thread going.
So, here we go.
Q: How many chapters should be covered in a semester (quarter) course?
A: My general rule of thumb is 3-4 class periods per chapter (I am assuming fifty minute class periods). Thus, in a 3-credit semester course (about 45 class meetings) I try to cover 12 chapters. In the past I have taught as few as 9 chapters, never more than 12. I don't think that covering all 16 chapters in the book is reasonable (the only reason the book has 16 chapters is to give instructors some choice).
Q: What are the precedence relations among the parts and among the chapters in each part?
A: Each of the four parts is independent, so the parts can be taught in any order. Within each part, the relations between chapters are more complicated. The following table summarizes my suggestions for each part. The columns show the suggested choices depending on whether you want to cover only two chapters, three chapters, or all four chapters.

Q: How do chapters (and parts) compare in their level of difficulty?
A: I feel that the most relevant source of information to answer this question is the aggregate opinion of the students in the course. At the end of each semester I give an exit questionnaire that includes several questions on the relative difficulty of the chapters–over the years, I have collected thousands of students' opinions on this matter. Here is a crude summary of what my students think (keep in mind that my students may be very different from your students):
(1) In ranking the difficulty of the chapters, Chapter 16 is considered the most difficult, followed by Chapters 4 and 15. The opinions on the easiest chapter are all over the place.
(2) Within each part, the last chapter in the part is consistently ranked as more difficult than the first chapter. This is true for all parts but the different is most significant in Part 4. (If you think of each part as a hike, each hike represents a slight uphill climb with Part 4 being the steepest climb.)
(3) When ranking the overall level of difficulty of the parts, my students rank Parts 1 and 3 as slightly more difficult than Parts 2 and 4, but the differences are not significant.
Q: Is there some significance to the fact that the book is organized into 4 independent parts with 4 chapters each?
A: While there is no compelling reason for a 4 by 4 organization, I like the flexibility that this format offers. In particular, I like the symmetry of having the same number of chapters in each part and the modularity of having four independent parts. For example, an instructor that wants to cover 12 chapters in a semester course can choose a 3 by 4 format (three chapters from each of the four parts) or a 4 by 3 format (full coverage of three of the four parts). The former approach offers a little more breadth, the latter a little more depth. I think that both approaches are consistent with the goals of a Liberal Arts mathematics survey course.
