I have to respectfully disagree about the Ethical Slut rec. It's interesting and has some great points, but I found it kind of preachy and self-righteous overall.
I have to admit that I read only a few chapters of it, so I can't really recommend the whole book; just the first few chapters. (Dorky attempt at a joke.)
I didn't find what I read to be preachy, but then, I'm also not poly or poly-curious. Maybe if I were poly, the book would have come off as preachy to me. (Lord knows enough kink books have that One True Way tone, and they make me want to heave.)
Still, I think that The Ethical Slut can be helpful as a sort-of guidebook (not rules; *guidelines* t /PotC ), especially for people who think they're poly but don't know what the best next step to take is.
(I blame all typos on The Boy's weird-ass ergonomic keyboard.)