These comments apply to any used book you might buy. You're finding them on the way to Amazon.com because Amazon pushes used books very visibly on their web site. If you are thinking about buying used, please consider the following:
1) If you shop around, you can often find this book new for the same price as many of the used books offered. The bookseller links on the home page will likely find you a similar price.
2) This book cannot be used without the CD. The CD Updates on this site are not sufficient to use the code or tools discussed in the book. Buying this book without the CD is a waste of money.
3) The software with this book is as valuable as the text. The included software is licensed only if you currently own a copy of the the book. The CD jacket is the shrink wrap: If the CD has been removed, you should assume that the software has been installed. You are encouraging software piracy if you buy a book in this condition.
4) That said, I have no objections to booksellers or anyone else with extra copies reselling a brand new book (implying an unopened CD case).
5) I am not compensated in any way when you buy a used book.
6) Amazon is not featuring used books as a goodwill gesture. The prominent placement of their used book links accurately indicates that they make at least as much, if not more, on used books as new books. Much of this profit comes at the expense of the authors and publishers.