I read the first book in the series, "Mirror Empire". It was a challenging book. This book drops you right back in the middle of the action with no recap, and I had a hard time remembering what was going on. There were lots of POV characters, all with alien sounding names, and the plot was spread out over several worlds without much overlap. I felt totally overwhelmed and confused. Generally I can mostly keep my feet even in books with a lot going on, but after reading several chapters I felt more lost than ever. And then I had to ask myself if I cared enough to keep going, and the honest answer was "no". I wasn't attached to any of these characters. I didn't remember their motivations or many of their conflicts, and while I'm clear on the overall plot of the books, I couldn't piece together this crazy quilt of narrative into anything resembling sense. It was exhausting and it didn't pay off enough for me.

Interesting new twist on the gateway trope. What would you do if you met your twin from another universe? Here the answer is clear. Eradicate them! There is a war for dominance of the lands that mirror the ones they came from.