I just finished reading all seven Harry Potter books. Amazing, incredible, creative beyond belief. It's not that the writing is complex; it couldn't be, otherwise all those kids wouldn't be able to read them. It's that the plot builds over the entire series, and every seemingly insignificant detail is carefully woven into the fabric to become an important point later on.
Obviously, J. K. Rowling either took Latin in school or has made a careful study of it. The incantations and spells are completely believable because they come from Latin roots and make perfect sense for what they mean. Expelliarmus is the incantation to disarm someone by taking their wand away ("expel"); lumos is for creating a light source; and levicorpus allows a wizard to levitate someone ("levi"