I know of no book on Metternich covering only the Napoleonic Years. Two that I would recommend are "The Final Act" by Gregor Dallas, Henry Hold, NY, 1996. It deals with the Congress of Vienna but details Metternich. It may also be titled "The Roads to Waterloo".
A second good on Metternich is his own "Metternich, the Autobiography 1773-1815, available in paperback. Ravenhall Books, 2004.