All the talk over a supposedly-major twist in the final Twilight film, out this week, has amounted to a little bit of nothing in terms of how the actual story played out, but gave the series's fans a good jolt of enjoyment and heightened the tension a bit, since most readers of the wildly popular series of novels likely went in thinking that they more or less knew what was coming.
It's also brought to the surface a long-simmering debate in the fan community of not just Twilight, but just about all of the popular serialized stories currently being adapted for television and film: How much change is too much?
It's a topic that The Walking Dead fans have been sharply divided on, especially this season; while in the past it's been easy enough to overlook certain tweaks to the source material on the grounds that "having Shane around makes things more interesting," this year has been totally off the rails. Characters are living and dying at different times and in different ways than they do in the comics, and the ever-present Dixons (who don't even appear in the books) seem poised to play key roles in the way the season will eventually play itself out.
True Blood's fans, of course, have been having similar discussions for years now; the novels by Charlaine Harris bear a strong resemblance to the TV series that's nominally based on them, but it's certainly not possible for an honest person to say that they "know how this ends" because they read one or the other of the Sookie Stackhouse novels.
Of course, television and the movies drive far more revenue and are seen by far more people than the average comic book or even a best-selling novel. Many of the fans on the inside are annoyed not only that changes have been made by Hollywood to pander to the outside element, but also that casual fans will likely see the "movie version" as canonical, replacing the version that inspired it; on some base level, the smaller, more dedicated group of fans see this as a violation of "their" material. It's a conflict that goes back for decades, since conservative filmmaker John Ford changed the ending to his film adaptation of John Steinbeck's The Grapes of Wrath.
(It actually goes back much longer than that, but the agitation among Steinbeck lovers is similar to what you see among comic book fans angry over the bastardization of Hawkeye in the Marvel Studios films.)
In seemingly all cases, the reasoning is two-pronged:
First of all, it exists in service of the story. If the writers think they have something better, they're likely to do it, especially in cases (such as The Walking Dead) where the original author is actively involved, pleased with the final product and maybe even would like an opportunity to revisit some missed opportunities. As often as not, fans of the source material get upset because it's not "right," leaving aside whether the changes do or do not work better than the stories they're replacing.
Secondly, as intimated above, the writers and producers don't want the fans thinking that they already know everything. Many of The Walking Dead's readers thought before this season began that they had a pretty basic outline of how it might play out in their heads (with the midseason finale being Rick and Michonne's ill-fated trip to Woodbury and the season finale being the big battle royale between Woodbury and the prison community, including the death of Lori). The decision to alter the fates of Lori and the baby has had ripple effects on those viewers, for whom it's much more difficult to guess what might have enough of an impact on the group to be the season finale following the events of "The Killer Inside."
These are considerations that are fairly unique to the kind of intricate, serialized storytelling popular in comic books, television and some series of novels. The James Bond films, for example, have always differed from the Ian Fleming novels...but most fans just shrug it off. After all, most if not all of the stories told in the James Bond/Jack Reacher mold don't rely on the previous installment to make sense.
The self-contained nature of those narratives means that only very basic things tend to carry over from one film to the next, rendering narrative changes more or less a non-issue for most fans.
That's true, too, for Breaking Dawn to an extent; being the final chapter, there's not a lot of potential for fallout.
The fans of the series have generally been enthusing about the changes made to the narrative, which is probably because it makes the story more visually interesting without compromising the basic message of the story's ending. Had they made major tonal or storytelling changes in an earlier chapter, it's probably less likely that the books's rabid fan base would have embraced the change the way they have.