Have there been any resources about spreadsheets that struck you?

I am pondering spreadsheets lately. I've realized that the graph shape of a sheet is sort of peculiar. I can't think of a lot of programming paradigms where I've bumped into problems structured this way.

I was thinking about spending some time reading about what powers spreadsheets and maybe trying to implement my own.

If you have any resources to share, it'd be very much appreciated!

Thanks.