I'm 99% sure there is probably a resource page tagged somewhere that is easy to find if you look for it, I'm too sleepy to though!
If I was to start from scratch, the book I would probably want to read first is "Opening Up: A Guide to Creating and Sustaining Open Relationships " by Tristan Taormino. I can't be sure it would be as useful if you are trying to convince your partner that they might be interested in poly too/explaining to them why it is important that they accept your desires, as it is for people who both want to decide how to go about it.
Note: on amazon you can read the first few pages. You might want to read through them and make sure it wouldn't be a detriment if your husband is struggling with stuff before you got it though...admittedly it turned me off when I started reading it because it made me think the focus of the book was about casual & group sex, and that it would give the world at large the perception that that's what poly is about.
Happiness will never come to those who fail to appreciate what they already have.