The Black Douglas by S. R. Crockett, Fiction, Historical, Classics, Action & Adventure

This story of life in Scotland during the 1400s focuses on the simple things: unrequited love, true love blocked by circumstance, arrogant ambition, and unbounded jealousy, all accompanied by vengeful feuding between individuals and clans who'd made themselves masters of the struggle for revenge. Budding romance here faces family quarrels and even international politics, with a French ambassador who's secretly a serial killer and the fate of Scotland as a free nation at stake. Justice, honor and devotion have seldom faced so many challenges all at once.
R. R. Tolkien credits Crockett as an influence on his wolf-fight scenes: "the episode of the 'wargs' (I believe) is in part derived from a scene in S. R. Crockett's The Black Douglas, probably his best romance and anyway one that deeply impressed me in school-days".