What kind of novels does J.K. Rowling have?

They are primarily classed as fantasy.
Sub-categories in which they could be included are:
  • Bildungsroman (the story of a young person growing up).
  • Allegory (because Harry Potter is a Christ-figure).
  • Detective stories.
  • Boarding-school stories.
  • Romance (this is a bit of a stretch, but the Ron/Hermione, Harry/Ginny and Lupin/Tonks story-arcs are romantic sub-plots).