It's hard to have the code compile after literally every single snippet. Sometimes, we need to change the signature of a function that already exists and is called, so there's going to be at least two snippets you'll have to apply before you're back to a working state.

It probably would have been possible to make this work by introducing temporary scaffolding code which gets removed shortly after, but it would have made the book much longer and more tedious.

Balancing thoroughness and brevity is always a challenge when writing.

The code is compilable at the end of every chapter and usually compilable at the end of every heading within a chapter. One thing I could have done that I didn't would be to place some visual markers in the book whenever you reach a point where things should be compilable. I'll keep that in mind if I write a third book.