Really?  You must be teaching in a far off rural area.  When I did multiple schools in the countryside both middle and elementary, it was hard to keep track.  So, I never used the book.  In the bigger schools and in bigger cities, they pretty much expect you to stick to the book. 

I didn't teach from the book. I was using it as a guide for the lessons that I'd prepare. The book was straight up garbage and its associated CD even worse, but I could use the phrases/grammar to make a decent lesson.

And, yes, I think preparing lessons that are based on what the students are expected to learn is important.