The book is well written and well informed (constantly more/better on Stalin than Hitler, constantly going deeper and more into subtleties in the personal level interactions, while the Nazi half stays more into general) but the comparative format (1 Hitler chapter, 1 Stalin and so on) is tiring and distracting. This could have been a good book (on Hitler) and an excellent book (on Stalin), but mixed together it turns mediocre at best.
A meandering flood of interesting little historical anecdotes, but going nowhere. There is no structure, central thesis or some overarching conclusions (as in Sapiens for ex.) and not even a clear stream of thoughts. So, good to grab the attention of high schoolers or first year students, but nothing more.
First 60% were 10/10, character driven, with some original concepts and good story (felt 90% like reading Abercrombie, just without his more Tarantino-esque humor/over the top occurences). Also good flowing writing and good rhythm.
Unfortunately, the last 30% are quite bad, 4/10 bad and consists only of "action! Action!! ACTION!!!" and bad at that also, since the character development becomes useless or even strongly inconsistent (Nancy) and the author is not good at writing battles, neither at 1st person POV, nor in the tactical view.
Will not read the rest of the series.
Might be useful to mention i read Iggulden before: loved the Genghis series, but disappointed with Lion of Sparta (mediocre to lame) and Dunstan (straight up bad).
In itself, it could have been a very good memoirs - the human side is honest and engaging.
Unfortunately, the book is slightly dragged down by the fact the author is not an intelligent person (naive at best, way less than smart most probably) and greatly dragged down by the strong propaganda content and approach, by the several episodes completely lacking believability (obvious and technically ridiculous lies, such as an already damaged ground attack plane shooting down 4 enemy dedicated fighters, alone, or 2 crappy I16 going against 6 much more modern Me109 and winning the fight, and more in this vein) and the typical hateful Russian schizophrenia: when a Russian shoots down Germans, great hero, amazing brave, what a guy and so on; when the enemy shoots down Russians, they are always "scum, vultures, jackals".
The enemy is also never Germans (or Romanians, Italians and so on) they are always all fully "Hitlerites, Fascists", and of course plenty of "scum", "crawling" and so on. Among those scum were my grandfather (returned, but fucked up) and grandmother's brother (KIA) and they never called the Russian enemy anything else than soldiers or humans, even in private talks, just like many other ww2 (Romanian, so Axis) veterans i read or spoke to, including ground attack pilots (so the exact same thing as Egorova, minus the blind hatred). They actually pitied those they bombed, while this author always and strongly enjoys it.
Overall, a potentially good book brought down by propaganda, ridiculous "hunter's stories" and blind hatred.
The story still holds up very well, with excellent gothic worldbuilding and characters and well maintained mystery.
The Victorian writing style, though, slow and protracted, with half the book made up from letters and diary entries and the dialogues few, short and far apart, is not that captivating any more for the modern reader, to be honest.