Middle-grade fiction is realistic fiction for elementary and pre-teen readers ranging in age from 6 to 12 with protagonists around the same age as the reader. For the younger readers, the books should be shorter (up to 160 pages or so), use large print, short chapters, and simple plots, and they rely heavily on dialogue, often with illustrations. (Heavily-illustrated beginning chapter books such as Dog Man or Bad Guys belong with the graphic novels). The characters should be involved in realistic pursuits (so, not Magic Tree House - that belongs with Speculative Fiction), in school or at home.
For other readers, stories are more involved than those in beginning chapter books, with more complex sentences and longer chapters, but less so than in young adult fiction. They can be adventure stories, coming-of-age tales, historical fiction, humorous narratives, mysteries, and sports stories, and are all set in the real world. In other words, there are no fantastical elements in this category of middle-grade fiction (ghosts, aliens, mythical beasts, mythology, or magic). Nor is there graphic sex, gratuitous violence, or an abundance of bad language.
Things to ask yourself when nominating a book in the Elementary/Middle-Grade Fiction category are: 1- Is this book realistic fiction about real-world situations? 2- Are the themes age-appropriate and relevant to the reader? 3- Is it a book that these readers will want to read and stick with to the end?"