Instrument Flying Handbook
Let's just say the manual that you better have is the FAA Instrument Flying Handbook, FAA-H-8083-15 reprint which supplants AC 61-27C. You will be expected to know this book forwards and backwards, chapter and verse.
Look at your CFI PTS. It will list all the references from which your practical will be drawn. FAA publications always contain everything it wants you to know, perform and teach. They are always the FAA final word.
Hope that helps. Good luck with your CFI-I.