When we watched the first Harry Potter movie in 2001, I concede that I had my doubts that the producers would be able to carry out their plans to adapt all of the planned HP novels, with the original cast. The first film was a big-budget extravaganza; and such productions take huge investments of time and money to produce. While the first film did extremely well at the box office, there was no guarantee that future films would duplicate its success (indeed, several of the movies earned less than the opening one, despite rising ticket prices), or that interest in the books and movies would continue to support film projects. Most of all, there was the challenge of the cast. Children grow up, and even when watching a fantasy film an audience would find it hard to accept a 30-year-old as a boy wizard. Moreover, a good child actor isn't necessarily a good adult actor. And children who act in films often put away such childish things as adults, and drop out of acting. The producers therefore had to craft seven (or, as it turns out, eight) high-budget, high-spectacle movies within a short enough time frame that they wouldn't lose their leads.
The films that have tried to duplicate the HP formula in the last several years have shown that this is no easy task. Numerous movies based on successful young adult series, such as the Lemony Snicket books or Phillip Pullman's series -- did not progress past the first film. Even the Narnia movie series, which met generally favorable reactions at the box office (especially the first movie), switched distributors, and may not make it past the third film.
Yet the HP producers pulled it off. Doing so took vast amounts of money (although the movies and related merchandise produced mountains of cash in return), multiple directors, and a cast that managed to grow into its roles. But the second part of THE DEATHLY HALLOWS opened this weekend, to spectacular box office (preliminary estimates are that the opening weekend generated nearly $350 million worldwide)and glowing reviews.
And, in fact, the final movie is one of the best. Although it would be impenetrable to a new viewer (or anyone who didn't see the first part), the movie is both a slam-bang action epic, stuffed with spectacular set pieces, and an emotionally-satisfying end to the series. The filmmakers did this not only by dividing the final novel adaptation into two parts (letting the story breath) but finding the dividing line in tone between the sections of the novel and sending the second film on a headlong trajectory that doesn't let up until the final denouement. Further, while retaining the most important beats of the story -- which, like most of the Potter novels, is essentially a game-like quest for puzzle pieces -- the filmmakers reworked scenes to make them more cinematic. In particular, the scene in which (spoiler) Harry and a weakened Voldemort finally go wando-a-wando is not the chatfest it is in the book. Instead, it is a headlong fight that calls to mind the climactic castle swordfights of swashbucklers from Hollywood past.
The result is unprecedented. The closest analogue may be the James Bond film series -- but that series survived only by changing casts and tone constantly; and it did not deal with the quandary of child actors.
So, what now? I don't know if J.K. Rowling will succumb to what no doubt is enormous pressure to turn out further adventures (perhaps some novels about (spoiler) those rambunctious Potter and Weasley cousins and their misadventures at Hogwarts); but even if she doesn't, I doubt this is the final adaptation of this world. Past works of British fantasy, such as the Lord of The Rings trilogy and those Narnia books, have been adapted into multiple live-action and animated versions, not to mention radio dramas. I wouldn't be surprised to someday see a BBC TV series faithfully adapting the novels, with a new cast; or a series of graphic novels illustrating the adventures in slavish detail.
In any event, we have seven books and eight movies (not to mention various ancillary works Rowling has written up) and unprecedented success in translating a young adult series to film.