It’s kind of hard to take a look at individual entries in the Kirov series once its formula gets going, but if I had to choose one, I’d say Breakout. At the very least, it’s emblematic of the series. The Allies in this timeline have launched an amphibious invasion France from the south instead of from the north like they did historically. My fear when I first encountered the Kirov series was that it just would be stuff like that, or even more minor ones like “oh, well there were two Tiger battalions at ______ instead of the historical one?”
Instead, we get, in this book alone, timeshifted nuclear warheads, nuclear warheads developed with future technology by Volkov, airships, more airships, a timeshifted modern Bundeswehr brigade that inexplicably fights for the Axis because the author wanted to wargame it, and of course the adventures of the ship itself and its crew. There are reasons why, in spite of the pacing on display here, that I really enjoy this series. And Breakout has all of them.