Re: Can anyone recommend a good book about the Italian Wars (1490-1550)?
'Renaissance Armies' by George Gush remains highly relevant even though it was first published a long time ago, and has useful information for all the key forces engaged in the Italian Wars.
Osprey have a couple of titles in their range eg: Pavia 1525
Also on the battle of Pavia is the Jean Giono book. Although published in 1965, and a translation if you are reading it in English, it is a colourful account which is worth having a look through - even if you just get it through your library system.
Helion books (www.helion.co.uk) have a couple of titles which are relevant - although neither seem yet to be in print.
For the period leading up to the Italian Wars, and hence providing the context in part for why Italy was 'as it was' in this period, I'd recommend 'Mercenaries and their masters' by Michael Mallett.