The Art of Insight in Science and Engineering: Mastering Complexity (2014) [pdf]

What are the prerequisites to understand this book? I feel very intimidated by some equations.

I went to graduate school at Caltech; my time there intersected with SM for about a year, but I only learned about that when he had already graduated.

In one of the rooms in the physics building (E. Bridge), there used to be a few shelves with old theses. While checking them out one day (probably trying to kill time before a seminar), I came across Sanjoy's thesis. It was a curious little thing, unlike any of the other theses I had seen---a bit of a hybrid between a PhD thesis and a textbook, and remarkably, very readable.

That thesis was, apparently, the first version of his now famous book, Street-Fighting Mathematics. After getting lost in it for a while, I went and asked the administrative assistant if I could get a copy, and she said nobody cares about those volumes on the shelves, and I could just take it if I wanted. I still have that copy with me.

One year I attempted to audit the (somewhat legendary) class that the book part of SM's thesis was based on---"Order of magnitude physics", taught by P. Goldreich and S. Phinney. Unfortunately, the lectures were in the morning, and I managed to wake up early enough only a few times, and dropped out afterwards.

I continued to collect material on related topics over the years, and am still hoping to use them some day in a course, together with SM's books.

Comfort with freshman physics and math is really all that's required.

You can always review those first.