Beyond the Highland Mist (1999) is the first book in Karen Marie Moning's Highlander Series.
A fairy bent on revenge against sixteenth-century Highlander hero Hawk sends twentieth-century American Adrienne de Simone through time to become Hawk's wife. Since every woman falls at Hawk's feet, and Adrienne disdains handsome men after a bad personal experience, seems like a definite recipe for true love to develop.
If you're looking for a comfortable, fun romance novel involving time travel and fairies, without any real twists or surprises, this book won't disappoint.
[As an aside, what is it with Scotland for being *the* setting of choice for time travel historical romances??]
My overall rating of Beyond the Highland Mist is a B-.