I gave my wife the "Ethical Slut" also. However, what she mostly took from it was that poly people are in it mostly for the sex. So I have been trying to convince her it is more about the relationships and sex tends to be part of romantic relationships. The Ethical Slut is more about nonmonogamy in general. So you may want to find her something a little more about polyamory itself.
I think if you want to talk about how you feel and how you change, just bring it up. A big part of polyamory is the communications. So no time like the present to work on talking about how you feel andwhat you desire.