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It's possible it was a book from the Destroyermen
series. They're set during WWII in a parallel world. The newest book is called Rising Tides so you could have seen that one. However, I have never read these books, only heard about them from people who have, so this could be something totally different from what you're looking for.
No, and I don't think it was part of a series.
I'd say that it was probably either Treason's Shore by Sherwood Smith, or A Mighty Fortress by David Weber. Both of them are the last book of a short series.
Nope. It had a reddish cover. (Yeah, I know, huge help :P) There might have been something about magic mentioned in the blurb on the back cover. Maybe. Maybe not.
I've deleted the "probably written fairly recently" part from the OP, since I looked up a few other books I remember being with it and, well, the publication dates varied.
Hell's Gate or Hell Hath No Fury by David Weber and Linda Evans, maybe? One universe with magic, one universe with science, both invade the same world through separate gates. Multiple communication screwups later, the two universes are at war with each other.
None of the covers I'm getting from a Google image search fit, so I'm going to have to say no. Thanks, though.
If we leave the fantasy out of it (you seem not to be sure), there is "The Storm Tide", which is about the Civil War.
That book is non-fiction though, isn't it? So that can't be it.
I know you said it's not from a series, but... Midnight Tides by Steven Erikson?
Alternatively and also in a series is Storm (To Green Angel Tower) by Tad Williams.
Both of them mention war and magic on the back cover, and both of them have red variant covers.
Looked up the covers, and no. I added some more description to the OP.
I was passing through an airport recently, and saw this book in one of the stores, in the fantasy section. I thought the title was "Tide Storm", or something like it, but apparently I was wrong, as my searches aren't finding anything close to it.
The cover was reddish and depicted some kind of scenery. What I remember from the back of the book is some mentions of war and - I think - some kind of fantasy world. I realize this isn't much to go off of, but any help would be hugely appreciated.
Additional cover description: There were some buildings on the front. They don't really stand out; the scenery just kind of blends together in a sunset-red haze. The scenery, or at least the redness, extends to the back cover as well. The whole cover is primarily red.
Edited by Twiddler