Mom and Dr. Chryssides corresponded. He's the author of two books on Witnesses. One isn't very good in my estimation. The other Mom reviewed mostly positively. But even I [I'm 15] can pick out the wrong statements in Knox and Chryssides' books.
Mom's review of Chryssides' last book https://truthhistory.blogspot.com/search?q=Chryssides
Mom found him helpful and in her "introductory essay" thanks him for his comments on two chapters of Separate Identity volume 2.