What is the theme in Interview with the Vampire by Anne Rice?

Other themes in the book, such as immortality and loss of innocence, are perhaps more obvious. Immortality is a curse to Louis. Although he has reached the pinnacle of human desire, eternal life, he has done so through the veins of youth. Like Goethe's young Werther he contemplates suicide but nevertheless he clings to his immortal half-life, damned