If you want to learn NPrinting 17, start here: What is QlikView NPrinting? ‒ QlikView NPrinting
If you want to learn NPrinting 16, start here: NPrinting 16 Training & Installation/Upgrade Information
and then go here: QlikView NPrinting 16 Tutorials by Subject
Qlik is also building a training course around NPrinting. Otherwise, I'm unaware of any books for the product.