I'm insufficiently nerd-sniped - what I'd really want is a book where every single mathematical expression is written in code, which I could manipulate. I'm thinking essentially of a book version of a Scrimba[0] course. I personally would love it to be in SymPy code, but I'd be happy with anything.
Something that drives me up the wall is just how sloppy math notation can be. Supposedly this pure discipline, but many authors use custom conventions all over the place, shorthand, skip steps, etc.
Give me some math code, where the end result has to compile. No sneaky tricks allowed.
[0] https://v2.scrimba.com/