Hi rack,
Welcome to healingwell.
I think you are a wonderful friend!
My idea is for you to get this book and read it together with your friend. It is an easy read and you can hop around to different chapters that best suits you & your friend's need. It doesn't have to be read in any special order although reading the whole book helps tremendously in understanding & living with someone who has bipolar. It is great learning for both of you!
"The Bipolar Disorder Survival Guide: What You and Your Family Need to Know
by David J. Miklowitz
Best wishes!