Is it OK for a Sensei to supplement his/her teaching with Aikido books on the market?
I generally classify the various chapters in any given Aikido book into categories like History, Philosophy, Spirituality, & Physical Techniques.
For my personal development & teaching, I would focus on History, Philosophy & Spirituality. I would also encourage my students to read these sections, but not the part on Physical Techniques.
I would ask them to leave the part on Physical Techniques to their dojo training.