Thanks very much, Travis! I also just received a very thorough review from a psychology major, whom I suspect is Ryan, so I'm very grateful for the time and energy you guys are putting into helping me perfect this. 
I'll certainly consider all of those suggestions in going back over the first four chapters. Actually, to address your concerns about Chapter 4, Chapters 3 and 4 were originally one giant monstrosity, and the division between those two became necessary. I hesitate to subdivide Chapter 4 further, but I see your points. As far as the advanced topicness, I figured I'd throw a bit of very challenging material in there among what I feel are relatively "trivial" examples to someone experienced to keep the more experienced readers on their toes and perhaps stretch the beginners to at least try to wrap their minds around a concept like recursion.
I'll certainly consider all of those suggestions in going back over the first four chapters. Actually, to address your concerns about Chapter 4, Chapters 3 and 4 were originally one giant monstrosity, and the division between those two became necessary. I hesitate to subdivide Chapter 4 further, but I see your points. As far as the advanced topicness, I figured I'd throw a bit of very challenging material in there among what I feel are relatively "trivial" examples to someone experienced to keep the more experienced readers on their toes and perhaps stretch the beginners to at least try to wrap their minds around a concept like recursion. 
