If you're looking for a good free
audiobook version of A Princess of Mars, I can't recommend this LibriVox recording by Mark Nelson enough. He was a fantastic performer, and I wish he had recorded more of the Barsoom books, because I would definitely continue on with the series in audio version if he had.On the Novel:
I picked up A Princess of Mars because John Carter was coming to theaters and I don't like to watch the movie before I read the book. It's definitely not the science fiction we're accustomed to these days - it's more of an adventure story that happens to take place on another world, the science isn't as believable or well-thought out as more modern science fiction. But overall, I really enjoyed it and will continue with the series... eventually.