A friend loaned me this book--
A Straight Girl's Guide to Sleeping with Chicks. (link to Amazon below)
I was involved in my first relationship with another woman... I kinda fell into it (I was dating her husband, and the three of us....) She was bi- and I started asking a lot of questions. One day she came back from a friend's house with this book...
One of the few books I've ever been loaned that I didn't want to return. I ended up buying my own copy.