Advice About Audiobooks

This isn't the first time I've considered the benefits of listening to audiobooks but usually I give them some thought, see the price of them and then end up looking at clothes on Zappos. However I'm back in training for a half marathon and feel like the time spent on long runs could be well used listening to podcasts or to something other than music. Which brings me back to Audiobooks.... (for me it sounds like the perfect combination of two of my favourite hobbies!)

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I have some queries though and am hoping you can help:

1. What are your experiences with audiobooks?
2. Is it worth buying into a subscription service such as audible.com or just buy per book from amazon or itunes?
3. Bearing in mind I like mostly legal thrillers, mysteries, police procedural, (and the occasional fantasy book if it's not tooooo weird) have you got any recommendations of audiobooks that you have really enjoyed? 
4. Is there anything I should be cautious or wary of? 

I know I'm not the only running crazy girl that loves to read ... I'm hoping one of you can shed some light on the subject and help me make a sensible move into awesome multitasking.