Stuff about Tolkien on Film
is now on Wikipedia.
Supporters of the trilogy assert that it is a worthy interpretation of the book and that most of the changes were necessary. ... Boyens once noted that no matter what, it is simply their interpretation of the book. Jackson once said that to simply summarise the story on screen would be a mess, and in his own words, "Sure, it's not really The Lord of the Rings ... but it could still be a pretty damn cool movie." Other fans also claim that, despite any changes, the films serve as a tribute to the book, appealing to those who have not yet read it, and even leading some to do so.
In 2005, the Mythopoeic Society published a volume of critical essays about the trilogy and its effects on popular culture called Tolkien on Film: Essays on Peter Jackson’s The Lord of the Rings.
David Bratman criticizes several arguments defending the films as adaptations, such as "It’s Jackson’s vision, not Tolkien’s", "But they worked so hard on it!", "It brings new readers to the book", "The perfect film would have been 40 hours long", and "The book is still on the shelf".
More about the book:
Cathy Akers-Jordan, Jane Chance, Victoria Gaydosik, and Maureen Thum contend that the portrayal of women, especially Arwen, in the films is overall thematically faithful to (or compatible with) Tolkien's writings despite some differences.
Dan Timmons writes that the themes and internal logic of the films are undermined by the portrayal of Frodo, who he considers a weakening of Tolkien's original.
Kayla McKinney Wiggins opines that the films misread and misinterpret the nature of heroes as understood in Tolkien’s writings and in his source material due to a shift in focus from character evolution to action adventure.
Janet Brennan Croft criticizes the films using Tolkien's own terms “anticipation” and “flattening”, which he used in critiquing a proposed film script. She contrasts Tolkien's subtlety with Jackson's tendency to show "too much too soon".
Are these good summaries? The editing history says they were based on the abstracts on the Mythopoeic Society webpage.