ItemSearch totally different from Amazon.com search - What am I doing wrong?

Question

I'm using ItemSearch in order to get a list of books ordered by 'salesrank' aka 'bestselling',

problem is that the books that pop up for any BrowseNode are totally different from the Amazon list.

Test Case Author:"J R R Tolkien", SearchIndex:"Books", Sort:"salesrank"

Using the API:

• J.R.R. Tolkien Boxed Set (The Hobbit and The Lord of the Rings)
• The Hobbit: 70th Anniversary Edition
• The Lord of the Rings: 50th Anniversary, One Vol. Edition
• The Legend of Sigurd and Gudrun
• The Silmarillion
• The Lord of the Rings
• The Children of Hurin
• The Fellowship of the Ring: Being the First Part of The Lord of the Rings
• The Return of the King: Being the Third Part of The Lord of the Rings

Using Amazon.com Adv. Search:

• The Lord of the Rings (Trilogy)
• The Hobbit
• J.R.R. Tolkien Boxed Set (The Hobbit and The Lord of the Rings)
• The Legend of Sigurd and Gudrun
• The Lord of the Rings: 50th Anniversary, One Vol. Edition
• The Silmarillion
• The Fellowship of the Ring
• The Children of Hurin
• Lord of the Rings, The
• Return of the King, The (Vol 3)

---

Help would very much appreciated