Using Windows XP – Book cost

Greetings!
In looking at your “Overstock Reduction Sale” listing ZDnet’s “Guide to Using Windows XP” was listed, costing $ 20. In clicking on the image of the blue book another image came up with a yellow book, titled CNet’s “Guide to Using Windows XP”, costing $ 10.

What is this all about? Same book but different prices — or different books and different prices — what is the difference in the blue versus the yellow books?
Looking forward to your answer / futher details!
FRED