Should the research proposal focus on expanding on the doctoral work (i.e. turning the dissertation into a book) or should it reflect a new project or direction in research?

In general, selection committees prefer to see a proposal that identifies a novel line of scholarship, extending the doctoral research in a new direction. However, in some fields or for some individuals, a proposal to complete or expand upon previous work might be favorably reviewed. In such cases, this should be combined with a plan for making a significant start on a new project.