How does your book compare with the classic "Operating systems design and implementation" by Andrew S. Tanenbaum and Albert S. Woodhull implementing MINIX?
MINIX book describes more practical designs, with a more feature-rich implementation. However, UNIX features such fork, brk, and tty are not intuitive for beginners. By writing a toy OS first, readers can compare the toy OS with MINIX, and understand that UNIX-like is just one of many possible designs. That's an important perspective IMO.
Also, readers can actually implement better algorithms described in the MINIX book. It makes the MINIX book more interesting to read.
The Tanenbaum book is great but it is a particle physics textbook compered to this OS cookbook.