I only have #1 and #3 - - Both great books!
What I found so revolutionary about the book "The Second Brain" is the concept that our guts, which are perfectly capable of operating independently of the brain, are also perfectly wonderful at causing immense suffering and stress TO our brain. Rather than the usual pablum we hear from our GI's and internists about how it's all coming from "stress" and if we would just calm down, "relax", take some anxiety pills or anti-depressants, our guts will behave. Dr. Gershon makes the point that when the bowel works fine, the brain can do what it needs to without ever having to expend any energy on thinking about digestive functions. However, when the bowel misbehaves, suddenly the brain has to spend an inordinate amount of time worrying about what might happen next. As the good doctor said in a TV interview, if you are chained to a toilet with bloody diarrhea, it's pretty hard to think about anything else. Now who here can't relate to that?