Historical fiction can be both educational and entertaining. As a former junior high history teacher, I know how valuable historical fiction as a secondary source can be as an educational tool. In my Colonial American History class for 7th graders, we read Johnny Tremain by Esther Forbes as an accompaniment to our unit on the Revolutionary War. The students enjoyed reading the story a great deal. It was a break from reading the textbook and other primary source materials, and looking at the era through the eyes of a boy their age gave the students something for them to relate to. It was much easier for my students to empathize with Johnny than larger than life figures like Paul Revere or George Washington. The kids thought that Forbes made the story very believable, but as a writer, I know that it is a hard genre to write in.
It's hard because of balance. Historical fiction requires a great deal of research, so some writers may want to pack in as much info and details as possible to convince the reader that the story is authentic. Finding that balance is something that I'm working in with my current story. Too many details will bore the reader, yet too little will make them weary of the accuracy. There's not necessarily a right answer, so it's something I'm really trying to figure out.
I wish I had Yoda in my corner saying things like, "Ehmmm, balance, yes!"