Defy Not the Heart by Johanna Lindsey

The first book in the Shefford series from #1 New York Times bestselling author of historical romance, Johanna Lindsey. 

Reina seethes with rage over her fate: taken captive by the knight Ranulf -- a golden giant of a man -- who has pledged to deliver her to the nuptial bed of the despised Lord Rothwell. She will never accept such bondage -- and Reina offers herself to her kidnapped instead, offering to make Ranulf a great lord...if he agrees to wed her.

But the brave knight desires much more than a marriage of convenience from this proud, headstrong lady who treats him with scorn yet makes his blood run hotter than liquid fire. She must come to him of her own free will -- or Ranulf will take her. For the passion that consumes them both cannot long be denied -- even though gravest peril surely awaits them on the heart's trail to a destines and turbulent love.