Prior to the start of the novel, Juliet wrote columns and a book under the pseudonym Izzy Bickerstaff. As the novel opens, she admits that the book she's working on—a book that would also be the work of Izzy—isn't going to happen; Izzy is no longer an interesting character for Juliet. Because of this, Izzy Bickerstaff comes to represent an old version of Juliet, while her decision to write under her real name and not use Izzy symbolizes Juliet's process of coming into herself. Because of this, it's telling that Mark mentions that he's interested in Juliet because of her work under Izzy's name—it shows that he doesn't truly love Juliet, he loves a fake version of her instead. Juliet's final decision to cast off Mark then completes her process of casting off Izzy and that identity, and instead, becoming fully herself.
Izzy Bickerstaff Quotes in The Guernsey Literary and Potato Peel Pie Society
I don't want to be considered a light-hearted journalist anymore. I do acknowledge that making readers laugh—or at least chuckle—during the war was no mean feat, but I don't want to do it anymore. I can't seem to dredge up any sense of proportion or balance these days, and God knows one can't write humor without them.
The simple truth of it is that you're the only female writer who makes me laugh. Your Izzy Bickerstaff columns were the wittiest work to come out of the war, and I want to meet the woman who wrote them.