The "short" part is really tricky. The number of books written about Napoleon is greater than the number of days since his death (which sounds implausible at first, but it's true, and the number of books easily outnumber the days). As a result, the short ones tend to be extremely specialised and do a deep dive into just one aspect, or if they try to be both short and broad they end up quite basic and I'm not sure if they'd tell you much more than his wikipedia page. His story is just so big and the views on him are so complex.

If you're looking for a biography, the shortest one I've read that covers most of the important points and that is also a good read is Andrew Roberts' "Napoleon: A Life" (in some places called "Napoleon the Great").

It's quite recent and up to date (taking into account the recent publication of Napoleon's letters). But it is only "short" in the context of Napoleon biographies, at 800 or so pages. I hope this doesn't look like I'm ignoring an important part of your question asking for short, but as far as this topic goes that is "short", as most of the good books about him are multiple volumes. This is well-written and a thorough read that will tell you what you need to know. One thing to keep in mind though is that some critics have commented that the author is too fond of Napoleon and too forgiving. I also felt a hint of that, so just keep in mind that this is written through the lens of an author who likes his subject and that there are many fair critiques to be made of Napoleon (but there's time to delve into that afterwards if this book gets you interested in learning more).

One other suggestion that fits the "short" requirement if you're not necessarily looking for a biography but more to understand why he was an important figure in history is RS Alexander's "Napoleon". I think this would be interesting for you if you've been reading up on WW2. It focuses on how Napoleon has been viewed in different eras and by different people since his death, how times and contexts have changed how we see him, and why he is sometimes compared to other historical leaders including some WW2 figures.