I dont have a book for you but one thing I would say is start thinking about the different activities you can have the patients perform to work on balance, endurance, mobility, etc. Once you start take some time to look at all the things they have in their gym and how you can incorporate them into treatment as well. You can work on straight forward ther ex and gait etc and that is important but mixing it up helps engage the patient and shows your CI you are thinking about different treatments to accomplish your goals.
I think most PT students and new grads are really lacking treatment ideas. Our schools are focused so much on evaluation and examination and we become very good at that but I dont think our schools do as good a job at teaching what to do after the diagnosis, especially outside of an orthopedic area.