From Goodreads "A Union regiment marches aboard a transport ship only to be buffeted through space and time and shipwrecked in an alien land, where these Civil War soldiers introduce unheard-of ideas of freedom, equality, and democracy"

I have listened to this entire series on Audible about a year or so ago. It's a fun portal fantasy/scifi alt history adventure. The author has a wonderful grasp of tactics aincent and relatively modern with the Yankees. The world it takes place on has many cultures from across history that were scooped up by strange cosmic forces and dumped into the world. It's barbarian alien hordes treating the tribes of man as chattle slave and food. The Yankees at the time of their arrival are the most technologically advanced. It's a great adventure read and the characters are endearing and you want to see them succeed.

All of the Tales Of The Primal land books by the late Brian Lumley are fun and avaliable on Audible as of my post. Fun Swords and sorcery adventure with a dash of cosmic horror.