Dragonfly2 gave some good advise. That is a good book and helped me to understand my wife's BPD.

Your significant other will have to understand that BPD is not curable and that if he stays with you, he has to learn how to deal with BPD. It can be as difficult for a spouse/significant other as it is for the one diagnosed, and it is critical for him to go to some counceling with you.

We bought our son (also BPD) the children's book Brandon and the Bipolar Bear. I got more out of that than anything else I have read!