Judging by the URL, this book was used for CMU's 15-151 / 21-128, which is a first-semester course for CS and math undergrads. Nowadays, the course uses [0].
If we're dropping links, here's the one [0] from my undergrad discrete math course that seems to have a lot of overlap with the topics in the CMU book. Our professor called it "notes" but it's more like a treatise...
That book was used in my "intro to higher math" class my freshman year. A very humbling experience, seeing that cover again gave me a bit of a knot in my stomach.
Every chapter of the OP book has an introduction which has the following subchapters: Objectives, Segue from previous chapter, Motivation, Goals and Warnings for the Reader. Which I really appreciate and I think its a great way to teach stuff, especially mathematics, since all those chapters contextualize the coming topic in various ways. (E.g. I imagine ‘Motivation’ does this with respect to the history and origins of the idea and ‘Segue from previous chapters’ contextualizes it with reference to the stuff reader has learnt so far. I didn’t read anything yet but it looks promising
[0] https://infinitedescent.xyz/