A dance of seven veils

I've read a couple books in the past year that have played with the idea of fiction through the use of layers of fiction. In both of these, a fictional author creates a supposedly nonfictional narrative of their fictional world, and then blatantly calls into question the veracity of that account. So is the novel that I (a supposed nonfictional reader) enjoy true fiction or fictional fiction? Or do double negatives apply, turning fiction into nonfiction? (ok, now I'm just being silly.)

The first of these novels is Life of Pi by Yann Martel, a truly superlative book. Was there really a tiger, Richard Parker? An orangutan? A biologically miraculous floating island composed entirely of carnivorous plants, populated by lemurs? (I think it's lemurs. John has my copy right now, so I can't double check.)

Today I just finished reading Ian McEwan's Atonement. I had a harder time getting into this one. The writing style really bugged me for the first 30 pages or so. Either it got better, or I became innured to it... Who can say? I ended up enjoying it as well, though not as much as Life of Pi. This book forces you to ask such questions as: Do Cecilia and Robbie really end up reunited? Does Briony ever really confront her sister?

The message that I took from both of these novels is that it's up to the reader to believe what he wants to believe. I wonder why authors do this. Is it a way to ensure a more than passing spot in the reader's mind? To keep the reader engaged and questioning long after they've read the book? Or is it merely to please the largest number of readers without issuing different editions with alternative endings in different cultures? How else to give Americans the happy ending they can't live without (and I admit, I might be one of these), while appealing also to more realistic sensibilities? Who knows. Both Martel and McEwan were very heavy handed with their questioning of fiction. I wonder if it could be done more subtley? Or would the message then be lost to oblivious pleasure readers (dolts?) such as myself?