If you're familiar with the origins of Book Creator, you'll know that Book Creator was originally developed for a child with dyslexia so that his family could create their own books to help him read. So it's no surprise that Book Creator comes with the Open Dyslexic font!
The next text box you add to the page of a book will remember the last used font.
Learn more about Open Dyslexic from the creator, Abbie Gonzalez.