Lady Mistletoe by Midnight (en Inglés) - Judith Lynne

Isabel's painfully aware that she's no one's ideal wife. After two failed courtships, she's accepted her place: a middling spinster from middling family, tucked away in a modest London room to fade quietly from everyone's life.

Though she's terrible at staying quiet.

All she wants for Christmas is one little book. Books are quiet. 

Bookshops, on the other hand, turn out to be quite a different-and alarming-matter.

The sharp young man who steps in to help doesn't realize Isabel's mixing in company far above her place. The longer their delightfully inappropriate conversation goes on, the more Isabel wonders how inappropriate she can be. 

She could never marry a lord. But the prickly, pained man under the mistletoe? He needs care, even love.

And those, she realizes, are gifts she's more than willing to give.

If this is Isabel's one chance for a connection of the heart, she'll be Lady Mistletoe by midnight.