Is it a good idea to do this? I'm a little unsure?

I think it is very creative! I know I would most definitely read it just to find out how the heck you could pull it off, without revealing too much. I think it would be a wonderful idea for narration, but it might be difficult. I mean, how do you tell everyone that the main character that they fell in love with throughout the books, wasn't really the one telling the story, despite it being their thoughts? If you can do it, I say go for it!