There are many books about the Kingdom of Neaples in italian language.
But First of all I advise you the three volumes of Virgilio Ilari-Piero Crociani-G. Boeri, "Storia Militare del Regno Murattiano (1806-1815).
http://www.libreriamilitare.com/prodotto.php?id_prod=36477&id_cat=161
Bye
Paolo