You do make a good point free2beme.
I understand that there have been several exposes and books written about the Church of Scientology; but do I care? No. That's because I never had any interest in Scientology, and I never will. But, I'm sure that most of the ex-Scientology members are reading them. If people already believe that a religion is strange or cultic, they probably aren't going to go out and pay 29.95 for a book that is going to tell them what they already believed. I think that this is why so many books about the Witnesses aren't even a blip on the radar screen.
As far as any books that are pro-Witness; I think that there are so few because there are so few Witnesses who are professional writers or journalists (if any). Another factor is that even if a Witness does have the professional credentials to publish a book; they will surely not write a book about the organization, because they would be strongly admonished not to. And even if they did have the tenacity to do so; I think many publishers realize that there just wouldn't be a very big market for it anyway.