Duff Cooper, Talleyrand, and J.F. Bernard, Talleyrand are dated, but quite good. In regard to Metternich, Alex Stavropolous is correct about E. Kraehe's work. Paul Schroeder, The Transformation of European Politics, 1763-1848 (Oxford, 1994) has very good chapters on Metternich during and after the Napoleonic Wars.

Best,

Rick Schneid