The book you are referring to is Copyrighted Siemens PLM courseware. Students are provided with a printed copy when they take the paid training class.
To find a training class, please visit http://training.plm.automation.siemens.com/index.cfm
Search for course name "Open API" or course number "13110"
Note that it is illegal to reproduce or distribute copies of the material you are asking for.
There is a "Getting Started with SNAP" guide that has been available for several years. Even if you don't use SNAP, this will teach you a lot about NX-based programming. Even without SNAP, you can still work through the tutorials. There is a free MiniSnap subset of this purpose.
Then, in NX11, there is a "Getting Started with NX/Open" guide that's similar.
Either one of these would be a good way to learn a few things and get started.