What was the point of having Faramir kidnap Frodo and Sam, and take them to something-giliath?
As with the first movie, Jackson doesn't really ADD anything, just moves the events and characters around some.
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Minas Osgiliath was the central city of the Kindgom of Gondor. Minas Anor was the city to the west of it, and Minas Ithil was the city to the East. Osgiliath was mentioned as having fallen to the Orcs in the first book (event moved to the second movie). Minas Anor was (long ago)renamed to Minas Tirith, and Minas Ithil became Minas Morgul when the Nazgul took it over for their fortress. Essentially, the west city becames Gondor's last hold, the central city was a wasteland, and the eastern city was the fortress of the Ringwraiths.
And, you'll note, in the book, Faramir WAS tempted by the ring. He just resisted. Jackson had a comment on that, that I agree with. Essentially, he noted that they've spent the first whole movie building the ring up as a manifestation of ultimate evil that corrupts all who may handle it....
It would be anti-climactic for Faramir to look at it, be tempted, and turn off right away as he did in the book. It had to be more of a struggle against the ring's evil. Of course, in the end, Faramir followed the book - he did what Boromir could not - let the ring go.
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Overall, it's a very good movie. Not as good as the book, but, well, duh. The book, when read (unabridged) takes up 16 hours of CDs. NO ONE will sit through that. Things had to be cut and moved for dramatic effect - to get the theme or emotion of a moment instead of the details.
And that, it did quite well.
NOTE:
Please do, when all the movies are done, PLEASE read the books. THEY ARE INCREDIBLE. (And probably, don't bother starting with 'The Hobbit'. It's a kids book, and a little less intense. Or, and skip the Silmarillion, as well. Unless you bore VERY slowly.)