This book was published second, after A Sorcerer's Treason. However, it's a prequel and should definitely be read before that book because the first book tells too much of the story in the second. You already know how the story ends so why bother to read it?
Ingrid Loftfield was a good woman, doing right by her parents, protecting her sensitive sister, and reliably completing her fair share of the chores necessary for life in their fishing village in 1872, on the cold shore of Lake Superior. Then Avan came. He said he was Norwegian, as many fishermen were. He was different – kind and quiet and strong – and one day he somehow, miraculously, helped to save her sister from a terrible fate in a watery grave.
She knew Avan was from a far land, knew he loved her. They would be married, have children…be fisherfolk as had generations before them.
But before they could wed, he was called back to the land of his birth, a land beyond the shore of Superior, beyond Earth, a magical land where he was more than a fisherman. He had to go. He wouldn’t see her hurt, and there were untold forces in his homeland, Isavalta, that could harm her beyond her wildest imaginings. But her love was too strong for him to resist. She would go with him, no matter the risks. So brave, so dear. Together they would face danger, and excitement to save an empire and its empress, and to find their own fate, no matter what peril, no matter how strange.
I'm currently reading Starship Troopers. Still!