Oh right, OP, brother.
Personally, I think there is a slight problem with how you've divided the chapters and sections.
If it could be divided in a more technical and user-friendly way...
For example: Introduction (used to roughly introduce the hardware setup, the intended audience of the book, etc.) Chapter 1 (with DOS startup as the chapter title, then giving a detailed introduction to some of the technical knowledge needed for the whole startup process, etc.) Chapter 2 (Introduction to DOS, then introducing a certain number of internal commands...)
Overall, it should give people the feeling that, facing a pitch-black monitor, I can use the book as a tool—I can either directly look up what I need, or study it systematically...