If you don't already know, Audible.com is a website that sells Audiobooks. It's $14.95 per month to be a member of the site (though they almost always have a free audiobook to start you off with) and each month you get one credit, which is good for any one audiobook that the site has. I believe that you can also purchase other books if you run out of credits after the month for the full price of the audiobook, but it can really get expensive. Do you think that it's worth the $14.95 a month just for one book? I mean I can get like 4 books on my kindle to read for that price!
15 bucks for an audiobook is an alright price if you need to get them somehow. I mean, seeing as the other books they sell for regular price can go upward to $50, it's worth. If you prefer normal books, however, you can usually get the book in paper for around 10 dollars or so, soooo... depends on which medium you prefer.
