Not necessarily. Larry King, arguably one of the best television interviewers ever, never read the books his guests had written. He felt his questions would be more genuine, without already knowing what was in the book. Plus, he said most of the audience would not have read the book either, making his curiosity more parallel to that of the audience. On the other hand, other great interviewers, (Oprah for example) always read the books their guests have written. So it really depends on the interviewing style of the interviewer.
Carly Schroeder was good in that episode too. Shame they never brought her back because of her legacy as well as the talent. Besides she wanted to come back according to SOD. Now since Carly is in the service. It's time to recast with a blonde in her late 20's to mid 30's to be Serena. They're giving more story to the non-legacy female characters i.e. Sasha and Willow than the legacy characters of Kristina, Molly, Serena, etc.,