Days 22-23 and I worked through getting "Hello World" on the screen using the code from page 81. Part of the reason it took so long to figure out was fighting the environment (both the Devpac Assembler and my understanding of what was supposed to happen). But I finally figured it out and now I have "Hello World" looking back at me on a Raspberry Pi version of the ZX Spectrum emulator. I would take a photo of it but unfortunately my phone is low on battery (whoops) and won't take the damn photo. You'll just have to take my word for it that I'm seeing "HELLO WORLD" on a screen and not imagining some form of Machine Code bigfoot on the screen.
I have to say that Toni Baker's book is quite simply the best book I have ever read for Machine Code. I wish she wrote for the Atari 8-bit as her style would have been an asset to the platform.