The only book I bought was the IMC Confuser. This helped for the exam.
My Instructor gave me a decent set of notes which helped. Ask your intsructor for if they have anything available or google and you may find some notes online. You will then be able to ask your instructor if it is suitable.
I should also add that I did occasionally dip into my ATPL notes to clarify a few things but I guess I could have used google for that.