Never read the book you are talking about: now I never will. Seems kind of like Dominic Deegan: Oracle for Hire without the pictures.
My oppinion exactly: with the exeption of a few scant tidbits taken from stuff that Rob and Jamie say, everything we know about Erfworld has been given in 98 pages. The series is progressing very well (heck, I would say that there are a few places that seemed rushed, and I would not have been the least bit saddened to see a few extra pages added in), and I doubt that anyone would complain if Erfworld were to be updated more.