Why is the CueCat "Modified"? 

The original, unmodified, CueCat barcode scanner was used as a marketting tool. It would re-direct your web browser to the barcode owner's web site. For example, if you scanned a can of Pepsi, you would go to www.pepsi.com. The scanners also (secretly) sent your scanning habits back to a central server for analysis. The modifed scanner disables all of that. It works as a standard barcode scanner. Data from the barcode is entered as if typed on your keyboard.  

Does the scanner read ISBN (book) barcodes? 

Yes, the scanners read ISBN barcodes but note that the number in the barcode (the number that's printed beneath the barcode) is not exactly the same as the text ISBN. The barcode number has a "978" prefix and the last digit (the check digit) is different. Software that is made to work with book barcodes compensates for this; otherwise, you may need to delete the "978" and change the last digit to use ISBN barcodes in your application. 

I want to buy more than one. How can I do that with your "Buy Now" button? 

When you click the "Buy Now" button, you will go to the ordering site (provided by a third party -- Paypal). At that time, you can increase your quantity before making your payment. Note that the shiping cost will increase slightly for larger quantities.