I have read the first three books in the series:
- Rally Cry
- Union Forever
- Terrible Swift Sword
An American Civil War regiment gets transported to a world where a savage species comes around every few years and collects tribute in the form of human flesh. This series trods a well-worn path of military sci-fi (a prime example is Jerry Pournelle’s 
Janissaries), Fortschen does decently well. The first book is not bad, but by the time I got to the end of book three, I discovered that the story was not really going anywhere anymore. There is better stuff than this out there.
