I just finished this one. A really excellent look via DBWI of the problems of AH, in particular of books like those in the What If? series (which I assume is what you are parodying/doing commentary on). You directly highlight some of this in the appendix, but what struck me was the conservative assumptions of many of the writers in treating various things that came later as fixed points in history (such as the Bloody Fifties) which, of course, are just names to the OTL reader until they're eventually described. That felt like a very accurate commentary on books like the What If? series.
Forgive me for sounding like a US TV executive, but my only concern was that it might be 'a bit too clever' for the general audience given the conceit isn't obvious from the title and you might get a load of 1-star reviews from twits saying well, actually, Chamberlain did resign, you know.