Whether you're conventionally reading the book or not, the effect on the brain should be very similar. We receive only the words and our minds are left to process the images actively on their own. This active process is bypassed in say, watching television. I'd say as long as this element is there, one receives the benefit (or its greater part) of actual reading. This would explain why reading to children is so helpful to them.

The only thing taking away from our experience in listening to audiobooks is that we can't be totally focused on them. I'm assuming people listen to them while some activity such as driving as I can't imagine one just sitting on a couch listening to an audiobook.

I used to do what you've described, but I went through the books too quickly and it was a bit too pricy to keep pace. An audiobook is so much more expensive than the used books I'm used to buying. (Do you get your audiobooks used?)

The vast majority are free on LibriVox, which are more than 2400 public domain works ready by volunteers. I also get some from the library and from friends and I subscribe to audible.com, which is a fairly cheap subscription fee.

I work at Barnes and Noble, and listening to an "eBook"we consider reading because it is still the act of gathering a story from a book, whether by visual or auditory. But I think that anything by auditory is a substanial amount harder to retain than visual so to me, physically having the book and reading it allows me to remember the story and also to be able repeat it to others.My last comment is that I would rather have the physical book in my hands than a gig on a electronic.

My wife has become a huge fan of the Kindle, and it's a lot more pleasant than reading on a typical backlit screen -- and she can take it everywhere without the bulk of lots of books.

I have thought of myself as a visual and not an auditory learner, but I find I'm retaining a comparable amount with the audiobooks (even when doing some additional menial task like driving). The one thing I lack with audiobooks is seeing the spelling of names, which is particularly important with French works (like from Dumas and Hugo) because even though I speak a little French I have difficulty "seeing" the word when I hear it pronounced.

This is an interesting subject. The two main issues that immediately come to my mind here are ones that have already been brought up.

First, you are right that the narration would affect the story. Hearing a voice is added information to the words, and I think can definitely affect one's interpretation of the material, depending on tone of voice, inflection, etc.

Second, there's just the simple issue of focus. It seems that when you read a book, there's a conscious effort to put aside time to sit down, open the book, and purely focus in thought on the material. Listening to an audiobook though, as you said, can be combined with other tasks, and I don't think this is as effective as reading just due to the fact that your level of attention is not as high. Not that it isn't possible...I suspect that if you were to close your eyes and meditate on an audiobook, your retention and understanding of the information could be as good, maybe better, than what you get from real reading. But one of the most basic things I've learned from psychology and my own experience is that attention level is incredibly important...many people may think they are paying attention, but there's that level of focus you can get to that really makes a difference in memory and understanding, which I don't think you can really achieve with 'reading' an audiobook, as long as it's accompanied by even menial tasks like jogging or something else.