Netezza books comes with the netezza product itslef. I am not sure any one uploaded on any site. If you are interested, I will send you the documents.
Netezza product is bundeled with both hardware and software. You cannot get the product directly. However there is an emulator in provided by IBM to learn netezza.
Search in google for netezza emulator, download the software and install it on your pc.
Could you share the document with me as well? My email id is email@example.com. I am am learning Netezza at my new job as well.
Thanks a lot!