+1 to OP's book, which is the best beginner guide I've found for understanding Beancount / plaintext accounting.
I was also confused about double-entry accounting for most of my life until I read the article, "Accounting for Computer Scientists"[0] by Martin Kleppman (author of Designing Data-Intensive Applications). It explains double entry accounting in a surprisingly accessible way by putting it in terms of graph theory. I don't even like graph theory that much or consider myself competent in it, but Kleppman's explanation was extremely effective.
I was also confused about double-entry accounting for most of my life until I read the article, "Accounting for Computer Scientists"[0] by Martin Kleppman (author of Designing Data-Intensive Applications). It explains double entry accounting in a surprisingly accessible way by putting it in terms of graph theory. I don't even like graph theory that much or consider myself competent in it, but Kleppman's explanation was extremely effective.
[0] https://martin.kleppmann.com/2011/03/07/accounting-for-compu...