Please note I am NOT an expert on this. I don't know how these photos were restored. But for example Criterion restores a lot of old films (including ones in the public domain)
Anyone can release these films (and that is why you see multiple bad copies of film in the public domain) but Criterion owns the restored version of the film and only they can release that version.
If the book is using the restored photos then I would have to side with Startrek history here. The original photos might be in the public domain but not the restored versions.
Though I admit this isn't what is stopping me from buying the book, its the price tag and no e-book version.