A LOT has happened since the screenwriter Steve Kloves began working on his adaptation of the very first Harry Potter book, “Harry Potter and the Sorcerer’s Stone,” in the late 1990s.
The three central characters — Harry (Daniel Radcliffe), Hermione (Emma Watson) and Ron (Rupert Grint) — have grown up on screen, enduring the twin horrors of Voldemort and adolescence before our very eyes. The stories have become progressively darker and more complicated. And Mr. Kloves has immersed himself so deeply in the world of Harry Potter that by the time J. K. Rowling’s seventh and final volume, “Harry Potter and the Deathly Hallows,” came out in 2007, he said, he knew the characters almost as thoroughly as she did herself.
Adapting the stories for film has been a delicate process all along, as faithfulness to books adored by millions has always had to be balanced with the conventions (and length) of Hollywood blockbusters. (Mr. Kloves is the screenwriter for all but one of the movies, “Harry Potter and the Order of the Phoenix.”) But “Deathly Hallows” was perhaps the most difficult of all. More than 700 pages long and crammed with quick-moving plot developments leading to an apocalyptic finale, the book ultimately proved too dense to make into a single film. So it has been split into two.
Part 1, to be released on Friday, covers the first half of the novel, a kind of prolonged road trip in which Harry, Ron and Hermione become nomads in hiding, sorting out their feelings for one another while eluding capture and searching for magical objects that must be destroyed before Voldemort (Ralph Fiennes) can die. Part 2, which builds to a final battle between good and evil inside the Hogwarts School of Witchcraft and Wizardry, ...