So while sitting there at anAnn Arbor coffee shop with dueling laptops (his a Mac, mine a Thinkpad, natch) I went to Amazon to check the sales rank. To my surprise I saw the book twice:
Click to see full-size screen shot
Now the funny thing is, Amazon lists the second editon first, ahead of the current third edition.
This is just fundamentally goofy. You would think that Amazon, of all companies, would "get" the importance of getting search right. As an author, you'd want to see only the current edition of a book. As a buyer, arguably there might be times when you explicitly want to buy the previous edition of a book -- but odds are you want the most recent, and that's the item that should show at the top of the hit list. Any previous editions should be labeled as such with links to the most recent version.
Also note that the most recent edition costs more -- 4 whole cents more -- yet the Amazon discount is slightly greater for the newest edition. Curiouser and curiouser...