Mixing history with fiction in stories has the positive side of making history seem less dry. Fiction can add drama and human emotions to historical facts. In 'Gone with the Wind', the historical backdrop of the American Civil War is combined with fictional characters' stories, making the war more relatable. On the negative side, when too much fiction is mixed, it can disrespect historical accuracy. It might also lead to the spread of false historical information if not properly noted as fictional, which can be a big problem for historical research and education.
One advantage is that it can make history more engaging. For example, in 'The Da Vinci Code', by mixing historical facts like the existence of the Priory of Sion with fictional elements, it attracts a wide readership who might not be interested in pure history. However, a disadvantage is that it can sometimes mislead people. Some readers may not be able to distinguish between what is real history and what is fictionalized, which could lead to a distorted view of historical events.