Price of a Princess: Mary Stewart 1

After young James the Third's accession to the Scottish throne, the
ambitious Boyd family of Kilmarnock seized power in a bloodless coup.
Mary Stewart, James' eldest sister, was at first unwilling to marry
Thomas Boyd, future Earl of Arran - but she had no choice.

Eventually, however, she learned to love him, and when he was sent to
the Danish court to negotiate with King Christian, she discovered a
unique talent for diplomacy. In exchange for Princess Margaret of
Denmark marrying her brother, Pr...