The books of Harry Potter, as we know, they open up a world that in the eight films of the saga is in some ways only touched upon: very little, for example, tells us about the film adaptation on the ghosts of the four Hogwarts Houses and their history, omitting details that are certainly interesting and sometimes quite dramatic too.
The films, in fact, are content to present us with only Nick-Nearly-Headless and the Gray Lady, namely the ghosts of Gryffindor and Ravenclaw, however, leaving out some very important aspects of their history: in the books, for example, we discover how the flap of skin that insists on keeping Sir Nicholas' head attached to his neck is the result of the badly sharpened ax that took care of his beheading.
The history of the Gray Lady, aka Helena Ravenclaw, is a wonderful blend of drama and romance: daughter of Hogwarts founder Priscilla Ravenclaw, ours stole the diadem from her mother that would later become one of Voldemort's Horcruxes. Having fled to Albania, the man who would later become the Bloody Baron, namely the future Slytherin ghost, completely absent from the movies.
Madly in love with Helena, the Baron ended up killing her following her refusal to follow him, only to later take their own life for remorse. The ghost of Hufflepuff is instead the Fat Friar, whose story is presented to us not by books, but by Pottermore: he is a former student of Hogwarts who opted for an ecclesiastical career, only to finish sentenced to death for witchcraft (his brothers did not like his ability to cure the most serious diseases simply by pointing a wooden stick at the patient).
Our advice to anyone who has stopped just to film, therefore, is to deepen as much as possible the world conceived by JK Rowling: we are sure you will not regret it! Meanwhile, let's see how the story between Harry and Ginny evolves over the course of the Harry Potter films.