I'm going to go out on a limb here and say that if this book exists, scanning it and putting it up on the forums would be a pretty big copyright violation, so don't expect that to happen.
However, if scripting is your focus, I believe there are some scripting tutorials out there, at least one of which is on/linked from Bioware's NWN web site at
http://nwn.bioware.com.
Also, if "learning by example" is your thing, you might want to check out Lilac Soul's NWScript Generator. It generates scripts based on a series of questions and scenarios. Granted these scripts are rarely 100% the way one might like them to be, but often it gets a scripter most of the way there. Also, it allows you to make a script that's most of what you need, look at it, tear it apart bit by bit, figure out how it works and tweak it to your liking. You should be able to find this on Bioware's site and the NWVault as well.
Lastly, check out the Neverwinter Nights Lexicon at
http://www.nwnlexicon.com/. It is a source for more complete documentation than Bioware provides along with examples, implementation notes, etc.
