Dr.R. M. de Vienne is not a 'he.' The R. stands for Rachael. She lives across the Columbia River from me, and I occasionally meet her for coffee and talk. She knows her stuff. I would have been proud to have had her as a student.
The errors in Chryssides' book seem quite minor, especially for a first edition of a book of this type. What appealed to me is the lack of drama. It's straight-forward reporting of what is. You see places where he disagrees personally with Witnesses, but he didn't write a rant, wasn't interested in making wild statements that sometimes characterize similar books.
Somewhere earlier someone made a comment about knowing all there is to know about Witnesses. That translates as "all I want to know." I was baptized in 1948 and served in various capacities. I still learn things. If you're not interested in learning, that's fine. I am.