Not a historian and not an expert by any means, but I found your post doing my own research into a similar question. I think I have figured it out (somewhat) in my research so I thought I would share to perhaps help you out. However, I have not read any of these, so I don't actually know about their content.

Andrew Roberts published a single volume biography in 2014 titled either "Napoleon the Great" or "Napoleon: A Life," depending on the market for which it was published/sold. See his site. You will see the two titles listed separately, but considering that they both won the same awards and the linked bibliography is the same, you can deduce that this is one book.

Adam Zamoyski published a single volume biography in 2018 called "Napoleon: The Man Behind The Myth" which is also sold in some markets as "Napoleon: A Life." You know this because on his official works page, there is only a single Napoleon biography.

Paul Johnson published a single volume biography in 2002 called simply "Napoleon" according to the bibliography on his official archive page. However, it seems that sometimes it is published under the title "Napoleon: A Life." (FWIW, this one is much shorter than the other two, at around 200 pages).

As I mentioned up top, I haven't actually read any of these, as I am also searching for an overview biography of Napoleon. So I can't really tell you much about the differences between what they cover, their perspective, their disposition, or their approach. But hopefully this helps you make a bit more sense of the various books and editions floating around on the internet, as well as structure your consolidation of people's reviews/recommendations.