Entrevista con el vampiro

The framing device gives a unique voice to the vampire's tale, but I wonder if it was always part of the plan or a later decision. How do you think it affects the reader's connection?

His loneliness and moral struggles are so vividly portrayed, but it also made me question what I would do in his place. Did others find themselves rooting for or against him?

The detailed lore adds richness to the story, and I'm curious whether Anne Rice developed the vampire universe in advance or if it evolved during writing.