This appears to have shades of Eric Flint's alternate worlds books. A WWII destroyer is transported to an alternate Earth, I think. On that alternate reality world a war is being waged by a variety of transported Earthlings and alien races.
This may be a good book but it is most definitely a sequel and there is a definitive lack of back story. The characters, races and alliances are totally confusing due to that lack of a back story.
This may be a good book but I can't really say as I didn't finish it. I got too frustrated trying to guess my way through the plot and characters. I like the writing style but there are too many other books out there that don't usually frustrate me.
This book may have been received free of charge from a publisher or a publicist. That will NEVER have a bearing on my recommendations.