So basically destroy the book so you can't resell it?
That is correct.
It's one of the tradeoffs of scanning using this method. The alternative is to use a book scanner. The service is expensive, but preserves the book. You could also build your own book scanner, but that takes time, money, work, and space for a larger machine. I didn't want to make a hobby out of it, and I didn't want to pay a lot of money to get them scanned for me when I could purchase a one-off scanner and do it myself. Pricing for services is pretty expensive:
http://www.blueleaf-book-scanning.com/book_scanning_service_order.html
To me, the value of a book is its contents (most books, anyway - other than vintage stuff or coffee table books, for example). Having the book instantly accessible and searchable when I need it is worth far more than a paltry resell price. Not to mention the reduced strain on my back. It's a matter of economics as well - lately my book bills at school have been over $500 a semester for
used books. I can resell to the school at the end of the semester for $20 each, or if I'm lucky maybe $50 to another study. Or for $3 on Amazon used books. Not a significant return on investment. However, since I'm paying hundreds of dollars per class, which is a significant investment for me, I'd rather have the book in a format that is easy to access, always with me, searchable, and not heavy in my backpack.
The workflow is pretty simple. Buy your books in the beginning of the semester and spend half a day scanning them. Every night when you get home, spend 5 minutes scanning your notes and transferring them to the iPad. All you need in class is an iPad, a notebook/pen, and perhaps a calculator or whatever class-specific tools you need. You'll never lose a document again, and even if your iPad is lost/broken, you have all your files backed up on your computer. It lets you be more organized because you don't have to hunt for papers - just look through your searchable, dated documents on your iPad.
It depends on what your goals are. If reselling is important to you, don't cut the books up. If your goal is to get through class without breaking your back and you want the convenience of digital books that aren't otherwise available digitally, this is a nice option, and it helps you stay organized.