The NAND to Tetris textbook is a masterpiece. (The book is called The Elements of Computing Systems: Building a Modern Computer from First Principles. The authors are Nisan and Schocken).

I worked through the entire textbook by myself, doing all the projects, and having no previous knowledge of computer architecture or compilers. It was a challenging but smooth process. The difficulty level was just right and I didn't get frustrated.

The computer you build is designed brilliantly. It's as simple as it can be, while still being a real computer can be that can play video games.

Im studying CS right now (community college) and we have two low level courses. In the first one we use Nand2Tetris and also build a SAP-1 (simple as possible) computer following Ben Eaters YouTube series. One of the coolest classes I've ever taken. We all built an actual working computer on a fricken breadboard.

The second class is the one im taking right now on x86 assembly and its cool but definetly not as fun as building a computer from scratch.

If no ones has watched Ben Eaters videos I highly recommend them.