I have used sections of Chateaubriand's "Vie de Napoleon" from his monumental "Memoires d'Outre-Tombe" and thoroughly enjoyed doing so. There are several free english translations online. Though depending on the scope of the course this may or may not do; we spent a deal of time on the French Revolution and then Napoleon, so the fact that Chateaubriand lived the time period and then reflected on it later made him ideal. He was an aristocrat who initially supported the revolution, only to become disillusioned and flee. He was initially rather taken with Napoleon as well, helping him win the favor of the Pope, only to again become disillusioned. However, without doing his back ground so students can understand his conflicted relationship with Napoleon, it might fall a little bit flat.

Another approach has been to use Juan Cole's "Napoleon in Egypt" to essentially encapsulate Napoleon's career into his Egyptian campaign. For instance, Napoleon has great initial success capturing Malta and then getting into Egpyt and winning the Battle of the Pyramids; however he loses a disastrous naval battle which costs him his fleet (Battle of the Nile), eventually his army is turned back and forced into full retreat (Siege of Acre), and then Napoleon leaves his army behind to rush back to France! The Egyptian campaign as presented in Juan Cole's book intentionally engages with discourses on Orientalism, French Republicanism, universal brotherhood, and the struggle of the French to be presented as liberators instead of occupiers. All topics which have remained relevant in the world today.

That said; Robert Asprey's "The Reign of Napoleon Bonaparte" might be easier for them to digest- especially if its a more entry level/lower level undergrad course. It is part two of a series and covers the Napoleon that they might already be most familiar with. Asprey is pretty clearly a bit of a fan-boy when it comes to Napoleon, but the book could get them talking about how/why Napoleon is remembered; how he wanted to be remembered; and how successful he was. Though as warning; the book is long... and that can be a huge turn off in my experience; especially for an optional reading.

A more modern publication would be Alan Schom's biography; it is a true biography, and gives equal focus to his campaigns and personal life.

It can get tedious at times during the early and formative years, and the author is heavily opinionated (alternating from viscous attacks on Napoleon's character to praise of his genius). This of course isn't a problem in and of itself, but if one of your goals is to have your students form and reach their own conclusions on the man, it may become problematic.

I provide a bit more detail viz. Alan Schom here, in an earlier post. I list some more issues I have with him; but ultimately, he's accessible, has good prose and is more often than not on the mark. A good publication all 'round.