As "novel" merely refers to a long-form narrative which can either be fiction, non-fiction, or a mixture of both, a "fiction novel" is an appropriate term that

As "novel" merely refers to a long-form narrative which can either be fiction, non-fiction, or a mixture of both, a "fiction novel" is an appropriate term that properly characterizes the novel as wholly fiction. See, for example, Truman Capote, who is considered the foremost example of the "non-fiction novelist".