Alessandro Beneditti saw the book, now lost for history, with his own eyes, according to his words:
...There were also precious books from the holy chapel, a plaque inlaid with gems and deserving of reverence for its sacred relics, and rings loaded with jewels. In that plunder I saw a book in which were painted various nude images of his mistresses, differing in appearance and age as his lust and insane love had impelled him in each city; these pictures he carried with him as souvenirs...From this account we can tell for sure that the book contained various nude images of women, differing in appearance and age. It is not clear if there was a text that explained in some way that those women were mistresses and the book was meant as souvenir or this is just the theory of the observer, who had attitude toward the King of France presuming his 'lust and insane love'. Benedetti apparently believes that the book was pained during the 1494/95 campaign.
It is a wild speculation, but maybe the VMs calendar pages, rich in nude ladies of various appearances and status (some crowned) may be the source of this first VMs theory. Starting with March (Charles VIII declared his intention to march to Naples in March 1494) and ending in December (He entered Rome triumphantly on December 31st,1494) the women in the calendar can be seen as pained in various cities during the movement of the French in the war.
Let's consider for a moment the circumstances in which the book was discovered. We have men in aftermath of a bloody battle:
... I saw corpses of brave men protruding at intervals which had been despoiled by many; the Greek and Latin soldiers had been first and had removed the more precious ornaments even from those still living, and then crowds of native peasants who had watched the issue of the battle from the summits of the mountains carried off the armor, and finally groups of servants and camp-followers removed the underclothing and left naked everywhere soldiers who were dead or half-alive... Very many wounded were found naked among the corpses, some begging aid, some half-dead. They were weakened by hunger and loss of blood and wearied by the heat of the sun and thirst; with tongues thrust out they begged for water. In this affair no form of cruelty seemed to be lacking... Some still breathed after hands and feet had been amputated, intestines collapsed, brains laid bare, so unyielding of life is nature. The river Taro carried very many corpses to the Po; the rest, more than twenty-five hundred, unburied and swollen by the heat of the sun and the rain, were left to wild beasts. Almost all of these had a piercing wound in the throat or on the face, but a few had been lacerated by artillery...
Not exactly a comfy place to analyze a book.
Plus, I can't find another example of such mistress-trophy book in 15th century. There are plenty of nude figures pained at the time, but usually in some religious context as excuse. Please let me know if there are surviving souvenir books of that kind from that time that I am not aware of.