Answer:
Probably, the creature see himself as a sinner, like the entire creation, but at the same time, he feels that there's still hope on the rendemption. But also, he sees himself as a creature that can be make several things, suffer, and still found hope in life.
Explanation:
Let's understand better. The question asks strictly about Paradise Lost, but I think we must analyze the creature's reaction based on the reading of the previous books - Lives and Sorrows of Werter. Well, the first one - Lives - is a biography selection of important Roman and Greek generals and politicians, and give us a feeling of importance, of inspiration to be better. However, when the creature reads Goethe, he feels depressed, just like Werther who cannot consume his love. Even so, the inspirations influenced by Lives are still there, and the creature continues his readings a bit better. But Paradise Lost, and the story of how Lucifer fall in disgrace, and the subsequent creation of the sin, the creature look at himself and think that as a mortal being, he can be great (like the personalities in Lives), he can suffer and almost give up like Werther, but he finds hope like humanity with the coming of Christ.