Audiobooks!

I ended up going with an Audibile.com Audible.com membership, since for the first three months it ends up being $8 per audiobook, and something like $15 afterwards (audiobooks are usually $30-$60). So for my next book I'm now deciding between "Seventh Son" by Orson Scott Card (Sci/Fan), and "The Planets" by Dava Sobel (she's usually a science historian, but this one has dashes of personal stories and philosophy and other strange things).

I may have read Seventh Son, or other books in the series, but I forget, and I don't think I did do this one, so I want to start (restart?) the series from the beginning. I like other Card, though his politicky ones I like less. I've never read non-Sci/Fan audiobooks before, and this one of Sobel's is supposed to be unusual for her, but I liked "Longitude" and loved "Galileo's Daughter."

Which do you think I should get next?