 Edward Duffy , an associate professor at Marquette University , says that one of the central characters of Chamber of Secrets is a book , Tom Riddle 's enchanted diary , which takes control of Ginny Weasley – just as Riddle planned . Duffy suggests that Rowling intended this as a warning against passively consuming information from sources that have their own agendas . Although Bronwyn Williams and Amy Zenger regard the diary as more like an instant messaging or chat room system , they agree about the dangers of relying too much on the written word , which can camouflage the author , and they highlight a comical example , Lockhart 's self @-@ promoting books . 
