The book Concrete Mathematics started as course notes for a class whose textbook initially was the (dense) "Mathematical Preliminaries" chapter of The Art of Computer Programming (Chapter 1 and roughly the first half of Volume 1), so it can be seen as an expanded and leisurely (and even more delightful, because of all the student jokes and other marginalia) version of that chapter. This is mathematics that Knuth needed for the rest of TAOCP.

So it's more "mathematics for the analysis of algorithms" (incidentally the title of another book by Greene and co-authored by Knuth), and so probably most applicable to the field of "AofA" rather than physics or computer science in general.

Lovely book, very few math books fill one with as much joy as this one.