Some recommendations via the Book List in the sidebar.

Especially: "The Campaigns of Napoleon* by David G. Chandler. If there must be a Bible about the Napoleonic Wars, it is this."

Although, of course, this isn't a complete list.

The Waterloo, and Trafalgar Companions are excellent military histories. They are focussed on the battles themselves, but have a lot of context as well. I found them very entertaining and informative.

Well, "The Memorial of Saint Helena" is an auto-biography of sorts of Napoleon (collected by a confident of his through their conversations).

It's important to remember that the napoleonic wars were both on land and sea. I'm biased as I love naval history but i strongly recommend you put as much time into understanding the importance of naval actions and blockades etc as for the land battles.