A unique, well-thought, and gripping read! I'm having trouble deciding how much I can/should say here, though the "added sf-f" shelf (referring to TonyD) surely isn't really a surprise given the premise. I won't spoil just what sort of sf-f is gradually discovered and explored in him, though.
You'll notice I shelved this under a number of elements, even where they aren't the primary focus, when I felt they deserved acknowledgment. E.g. the way Steve's attitude of moral superiority even in ignorance is addressed (to make *him* think, and grow, not just with anger on both sides) makes it a fixit for much of the messes in CW and beyond. And dear JARVIS is treated by *both* Tonys as the person he is, so AI shelf, check.
I wasn't sure about TonyD/Thor, never having seen it before, and when Thor finally returned to "Midgard", fairly late in the story, it was the sudden sort of involvement rather than my preferred slow-burn, with Tony at first not realizing how serious Thor already was, but I was won over by its further development and by the handling of certain revelations.
And speaking of revelations, there's an utterly brilliant one which I say could be canon, re. one key thing Hydra did with/to James Barnes, but I mustn't spoil it! It has emotional repercussions for more than just him, again very well crafted.
TonyD's career took a different turn here, and he has a highly respected if ultra-classified position based on his skill with intel analysis and synthesis, having left NCIS for Homeland Security with Morrow. Fury's meddling is infuriating, so sure his own priorities are the most important and his plans (machinations) are the only ones that will work (even with his organization riddled with evil and his own intel analysts proven grossly inferior), but he gets well-foiled in the larger view, even if not in time to prevent needing major adjustments to Tony's organization. I guessed who one of Tony's analysts would be, and she's a delightful addition. Natashalie, OTOH, is (I think *fairly*) depicted as not truly trustworthy, due to the damage done in her childhood, and her true limitations as both operative and analyst called out, including forcing Coulson to recognize with regret how she'd primarily been used for her sexuality.
Let's see, what else can I add, to not leave off on a downbeat note? Oh, the Hulk! He makes a sweet appearance, protective w/o rage, where he shows the connection he feels to his serum-"family". The tone of the story overall is warm and hopeful for all the protags (e.g., TonyS and Pepper are successfully rebuilding their friendship after their pre-story romantic breakup), *of course* not neglecting the humor and sass to be expected with the Tonys involved.
If I think of anything else worth mentioning (and safe to do so), I'll return and add it.
(I'm spoiled by AO3, where I can download a whole story, instead of sites like Jilly James's, where all I can do is save-as-HTML or print-to-PDF each section — and not even that on my tablet (some problem with the graphics loading), so I have to go to my Windows laptop. *sigh*) (Minor update w/reread 6/'22: I now *can* print-to-PDF from jillyjames.com on my Kindle, so the glitch must've been fixed.)
One additional note as of my 5/2024 reading — I really didn't plan to reread the whole thing again, btw, but... ¯\_(ツ)_/¯ — I neglected to mention how the "two Tonys" situation is handled. Answer: it depends on the PoV of each scene. Steve, for instance, thinks of TonyD as Anthony. TonyS is always either "Tony" or "Stark". It's occasionally, unavoidably, blink-a-couple-times-to-reorient confusing, but not too bad.
2/2025: Less than a year again! Apologies to my review-followers. I'm really not giving you much new lately, am I? For better or worse, it's not premeditated — I saw someone suggest that some book-[talkers'] repeated reads were deliberate to artificially inflate totals, but I'm just a disorganized mess who sees a file or link and can't resist opening it again, despite already having WAY too many open browser tabs in progress and all.