Sometimes is difficult to come up with a good title.

If Harry returns to the wizard world he is taught by his headmaster. Together they go in search of the Horcruxes to destroy them, so that Voldemort become weaker.
This year, has Harry not chosen for Potions and he is told that someone else takes these lessons. Professor McGonagall he has to attend courses to achieve its end goal, as Harry find a book that is area dedicated to the Half-Blood Prince. Together with his friends they try to find out who this is.

Harry Potter and the Half-blood Prince is a good intermediate piece for the end of the story.