I am mainly looking at the political side of it and have looked at some books on Renaissance diplomacy. I've requested The Italian Wars 1494-1559 by Christine Shaw and have started looking at Sack of Rome by Luigi Guicciardini (well, the translated version) and The Black Bands of Giovanni: Infantry and Diplomacy During the Italian Wars by Maurizio Arfaiol.
The Italian Wars by Shaw and Mallett are the good thing. Incredibly informative and the book has a really useful bibliography for going forward. Mallett's Mercenaries and Their Masters helps to paint the background for the wars, I really recommend that too.