This is Crigger's fifth book about gunsmith Boothenay Irons. The previous four stories had her time-tripping into trouble. Always, it was related to an old gun. This story is a bit different. Instead of going to a different time, she is kidnapped to a steampunkish alternate America. (Not a spoiler, as that is almost the first thing you find out in the story.)
There she finds herself in the middle of a bloody power struggle. If she wants to get back to her own world, she will have to help one side or the other. She had better choose right; her life depends on it. Lots of action, quite a bit of humor, and even a little romance: good book.