I only ask because I joined up last year (to get a free iShuffle thingy) and got the 'plan' where you pay £15 per month and get 2 audiobooks.
At first sight the website seems a bit impenetrable (it's not v well-designed and if any of you use Lovefilm - now that's a good website) and to my horror there seems to be a lot of religious literature which I don't get at all. Also there is a lot of American stuff which isn't my taste either.
However I have had two audiobooks a month, or recordings of comedy shows, and it's been brilliant.
They don't make it fantastically easy and there's a lot to put you off but if you trawl through, there are some great books to be had. Highly recommended.