Style isn't copyrightable, there has to be more substantive commonalities than just that.

It'll be up to the courts to decide if there is, of course. I notice that a review of the book quoted Ackerman from it:

In cases where the historical record is unclear, or when my interviews conflicted with previously published accounts, I’ve attempted to recount the most likely version of what happened, based on research and my own conversations with many of the primary participants. A certain amount of historical interpolation was required to offer a clear narrative understanding, including into the thought processes and motivations of those involved.

Which suggests that the book is partly fictionalized, so it's possible that there may be identifiable elements lifted from it. We'll see.

I agree that, if these allegations turn out to be true, it’s pretty damned scummy. but is it copyright infringement to tell a story from a certain perspective?

I mean, I’ve seen the film, and I’ve skimmed through the book. they both focus on the most interesting parts of the story as any dramatic retelling would, and the story itself lends itself to a certain interpretation, regardless of who writes about it. Personally, I don’t see the story bing told (at least from the protagonist’s perspective) any other way and there are certainly many differences between them that are immediately evident. But it would seem to me that anyone telling a story about those events would end up with a similar story simply because they’re based on real people and historical events.

but you’re right that there’s probably enough “there there” to warrant adjudication and would depend on the interpretations of copyright law by the judge and jury, if it were to go to trial.

edit: btw, your use of a musical isn’t a great analogy since musicals have way more original material (the music) tat can be used to prove or dispute a copyright infringement claim than simply interpretation of an historical event.