The Twelve Days of Seduction by Maire Claremont

Adriana has a quite a few secrets about her past - a past she wants to leave behind and live as a governess in Alexander Hunt's household. But Alexander has found out her secret and is threatening to throw her out into the snow - and right before Christmas. He's willing to compromise and let her be his mistress instead though (how generous).
While he sounds a bit like an old fashioned pig, he really is a very good guy that wants to keep Adriana in his life, even if she isn't suitable for employment as a governess. They begin a little game and it gets quite interesting. Adriana has quite a mouth on her when she has an important opinion and she's astonished when Alexander actually backs her up on many of them.
This was a very sweet holiday story and I loved the Christmas scene with everyone opening presents. It really let you see into their personalities.