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.