I found Elting's Swords Around a Throne to be very readable and quite illuminating. The book is not about Napoleon himself but rather his tool for conquest, the Grand Armee; how it was recruited, organized, equipped, cared for medically, and a lengthy chapter describing the marshalls that led it.

The Campaigns of Napoleon by David Chandler is the foundation for most english language readers.

Claus Telp's Evolution of the Operational Art: 1740-1813 is a really clearly written work that'll help one conceptualize Napoleon's campaigns.

Michael V. Leggiere's books, including Napoleon and the Struggle for Germany in two volumes, and The Fall of Napoleon explore the German campaign of 1813 and the invasion of France in 1814 respectively.

Thunder on the Danube is a three volume work on the War of the Fifth Coalition.

I also recommend On Waterloo: Clausewitz, Wellington, and the Campaign of 1815, edited by Christopher Bassford; it contains Clausewitz's analysis of the battle, the Duke of Wellington's response, and interpretive essays by scholars.