Chapter 3 talks about McCulloch-Pitts.
I remember being impressed with chapter 14 ("very simple bases for computability") as a kid. Finding UTMs with minimal number of states etc. are great riddles. I also fondly remember the discussion of the halting problem and related problems ("does program P output X") in chapter 8. This was my first introduction to this procedure and Minsky made the idea of reducing one problem to another totally straightforward. Many years later I realized that not a few CS students find these ideas confusing.