As @David Flin has highlighted, some of this review was rather shall we say, cathartic for me to write as a long-time Alternate History fiction reviewer. However, I'd also like to frankly highlight just how good this book is. It was genuinely like a breath of fresh air compared to many of the AH titles I've come across in the past year - inventive, original and actually well-written.
If there's ever an SLP Book Club, this would be the first title I would recommend because there's so much to discuss here, both that unfolds within the book itself, and also lots of stuff that is poised to come up in the next book in the series, which I believe is due in the next six months or so.
Without trying to use spoilers:
The actual PoD(s) for the change in history are not only original, focusing on a front in the First World War that's barely ever considered despite the blood shed by Italian and Austro-Hungarian forces;
The way that the timeline has shaken out after a Central Powers victory is fascinating, because it's like Kaiserreich but without everything deliberately dialled up to 'Fucked up beyond belief'
You've got a France that has been forcibly neutered, once again, and seething under economic sanctions; a Britain that has basically gone 'Well we didn't care about Europe anyway' and focused purely on Empire and gone weirdly isolationist
A USA that never got dragged into the conflict in the first place, so is just sort of on the sidelines wondering what it should be doing
A dominant Germany, of course, but cleverly we never see the German PoV, which would be so cliched; instead we see how everyone reacts to German hegemony
In fact the best bit of the book, by far, is the focus on Austro-Hungary. You get a real sense that everyone realises that it should have collapsed decades ago, or during the conflict; but then it suddenly won, and even gained Italian territory as compensation for wartime losses, which has only caused greater internal and external burdens. What, exactly, the Empire is supposed to be doing by the 1930s is a huge open question, and there's a lot of soul-searching amongst the Austro-Hungarian characters as to how the Empire goes forward
There's so much potential, especially as Germany and Russia appear to be on a collision course over the Ukrainian DMZ, that I genuinely can't wait for the next title