Step 10 to GTD Mastery is: I have listened to GTD on audiobook.
It was interesting to listen to David speak to me, but there isn’t any content that can’t be acquired by just reading the book. For anyone just getting started in GTD, I recommend buying the book because I found some of the concepts of GTD are better explained visually (e.g. a tickler file).
The abridged version that I listened to clocks in at under 3 hours. The big picture is there, but I couldn’t help but feel that finer details were missing (TBD upon a re-reading of the book). However, there’s a newly released unabridged version of the audiobook. According to the DavidCo site, this one clocks in at 8 hours and contains all the material from GTD.