"Mastering the CCNA" Chritopher Parker
Meanwhile, the search lead me to an interesting page on Apple's UK site, the "iTunes Store Top 10 Audiobooks - Technology". Interesingly, the US site doesn't appear to have this chart, yet the UK site includes the US statistic as its first listing. Additionally, I'm not sure what the interval is for the statistics. Still, it's an intereting chart and has some good audio books listed.
*20110825 - I looked again today at the page and the statistics have changed. I suppose this means the updates are daily.