I really like this book, is more than a refresher imo, it really goes from NAND gates all the way up to building a CPU using a Verilog-like language, its assembler language, then a higher-level language, etc.

The only thing that is not as nice is the tooling, it's GUI based and uses Java. One of the projects on my backburner is to attempt to write a better toolset for it. Or maybe I should just wait for someone else to do it haha (to be clear, there's nothing wrong with the existing tooling, I'd just rather something not based on Java that I could run on a normal IDE, say, VS Code).

That's exactly why I built my own tooling when going through the book. I built everything in Golang and am working on some visualisations in Javascript. Repo: https://github.com/deosjr/nand2tetris Website: https://deosjr.github.io/ (lispmachine part is wip)

One thing here that was genius is the supported assembly language. It has only 2 instructions, and they map directly to the hardware: load a value, and do an ALU/jump action. I never imagined you could get the idea of assembly simplified as bare bones as this.