Re: SciFi Channel version
"Well LoTR didn't have anything added that wasn't in the book (including the appendices that is) although it was messed around with for reasons I've never been able to understand, despite Jackson stating why he gave Arwen a much more prominent role in the film than she had in the main part of the book."
From a radio interview I heard some years ago (might have been Jackson), they had to cut loads out to make the story fit, but some of the scenes and characters which had to be cut did actually have a some important lines. Where those lines were needed for the plot, they were put into the mouths of other characters.
Even a normal sized novel, when read as an audiobook or dramatised in full, if often 20+ hours of listening time. To make film true to a novel, the added visual medium can let you cut out a lot of descriptive text, but you'd probably still need something like 10 hours of viewing to do an uncut film