Sometimes the fans have a point in complaining about changes, such as when producers decided to change the character of John Constantine from a free-wheeling, morally ambiguous London based Occultist into a surly, reluctantly heroic Los Angeles-based Exorcists. As well as the notorious changing of Harry Potter & The Philosopher’s Stone to Harry Potter and the Sorcerer’s Stone for the U.S. market, it being assumed that Americans were unlikely to know what a philosopher is. A lesser known controversy is when, for marketing purposes, the name of Stieg Larsson crime
novel Men Who Hate Women was changed to The Girl With The
Dragon Tattoo for the North American market, open references to misogyny, while a major part of the narrative, being considered a bit too distasteful for non-European readers. Which only goes to show that the literary world is also not immune from egregious changes.
Not all changes are for the worse either. Generally, authors know what they are doing when composing their narratives though, as mentioned, literature in the modern context is fairly open, not only in terns of length and depth of narrative but the sort of topics covered and how they end. Anything really goes in terms of novels and largely comics, both of them having let go of the notion of the Happy Ending as the only real option. Films, for the most part, have not. There are, of course, exceptions such as American Beauty, Leaving Las Vegas and just about everything Alexander Payne has ever done. Though such films tend to be seen as "downers" and while usually critically acclaimed don’t tend to play as well with audience, who tend to be looking for something a littlemore upbeat. As demonstrated by film such as 28 Days Later, Taxi Diver and the Troma Studios classic Tromeo and Juliet which had their original endings changed because either producers or test audiences thought they were too dark. There are also cases, particularly in terms of comic-book to film adaptations, such as Kick-Ass, Kick-Ass 2 and The Losers the changes that were made are the things that the film audiences liked the most, making the film versions better over all. And not all changes are nessicarly bad or unneeded even if fans if the original work do not like them. Such as in the the case of Watchmen. Assumed for years to be “un-flimable” by many, including and especially original author Alan Moore, despite rumors of a film adaptation beginning soon after the original release of the books in the late 1980’s, the results astoundingly good and faithful to the source material. Despite this, there was still much discontent among fans of the comics because of a slight change to the ending. One which makes perfect sense in the context of the narrative, is in no way an ex-machina, has no real impact on the overall message of the narrative, was clearly done for budgetary reasons and was not something that someone who has not the books would even notice.
In all, whether or not the book is "better" than the film adaptation really depends upon on what one is looking for from the narrative. Though really, if all you want is a story that is just like the source material you would really be better off just reading the book and not bothering with any of the adaptions that might come about.