Turning a book into a movie often means either stretching the story across numerous films, or leaving chunks of it on the editing room floor.

"The Hobbit" director Peter Jackson seems to have gone with the first option, as he tells CNN that he wanted to bring J.R.R. Tolkien's prequel story to life with a hope to accommodate all of the memorable scenes.

(This might be part of the reason why we're getting a trilogy, with the first installment, "The Hobbit: An Unexpected Journey," arriving in theaters on Friday.)

"We are fans of the books ourselves," Jackson told CNN. "You can't ever faithfully adapt a book in the sense of just every line of dialogue and every scene as exactly the same, but you do try to take care of those iconic moments. The moments where, as a reader of the book and fan of 'The Hobbit,' you expect to see in the movie. You try to have all those moments in there."

Attention to detail also influenced Jackson's decision to use the high-definition format of 48 frames per second, which is double the standard.

Using 48fps lends "a sharpness, because you don't have the motion blur that you get at 24 frames," Jackson told CNN. "We've always taken great care to make this [filmed] world of Middle Earth very lived in and very authentic. It's nice to see all that detail on screen."

But if you're not a "purist," said The Hollywood Reporter's Todd McCarthy in a review, that commitment to the minutiae of Tolkien's universe may seem unnecessary.

"Jackson and his colleagues have created a purist's delight, something the millions of die-hard fans of his 'Lord of the Rings' trilogy will gorge upon," McCarthy said. "In pure movie terms, however, it's also a bit of a slog, with an inordinate amount of exposition and lack of strong forward movement."

New York Magazine's David Edelstein found "signs of bloat ... everywhere," while Slate's Dana Stevens deadpans that "the movie starts to feel like some Buddhist exercise in deliberately inflicted tedium." The screenwriters, Stevens added, "vastly [overestimate the] audience's need to witness every micro-bump in the road to Erebor. It provides service for the hardcore Tolkien-head, but no foothold for the casual fan."

Variety's Peter Debruge found that "The Hobbit: An Unexpected Journey" "delivers more of what made [Jackson's] earlier trilogy so compelling - colorful characters on an epic quest amid stunning New Zealand scenery." And yet, "it doesn't offer nearly enough novelty to justify the three-film, nine-hour treatment, at least on the basis of this overlong first installment."