The Hobbit film trilogy is often seen as one of the most irritating film adaptations of a book. Seen as a commercial grab for money where three long films were created from one short book, knowing that the large fanbase of Lord of the Rings would willingly go to see it. In this sense it was a success as it made a lot of money at the box office. Yet it still irritated the many hardcore fans of the original book version and Lord of the Rings trilogy. There were many countless changes that it would be impossible to cover all of them so I will discuss some of the worse changes.
The main character Bilbo Baggins is very different from his version in the book. Where in the film he is seen as adventurous, courageous and willing to fight and participate. However in the book his character contrasts this quite a lot as he is not an action hero. He is a thief for Gandalf and not a warrior. While the characteristics of certain characters changing can be annoying it's not quite as annoying as the vast amount of characters that were added either because they were popular from the Lord of the Rings trilogy, or they just needed extra characters to stretch the story into three films. For example the main Orc, Azog the Defiler, hunting Bilbo and the dwarves, was never in the book. He is simply an extra character that is there to provide another story arc from the main one, as the main one doesn't have enough content to warrant this much screen time. This is not the only extra story arc that has been added in to fill out the film. Romances between characters that were never written about appear. Legolas, who is a character from the Lord of the Rings trilogy, appears in the Hobbit series. This is likely because he was one of the more popular and idolised characters from the LOTR. Another character that didn't appear in the book is Radagast the Brown, another wizard to again fill more meaningless content in the film. Although I have only given a few examples there are countless more to display how far this derives from the original source. While all these characters are being added, an important character from the book, Tom Bombadil, does not appear at all throughout this trilogy.
It seems like this film series was unable to capture the reality of the book. Where the book was quite childlike and story driven, the majority of the film adaptation was endless fight scenes twisted in with meaningless story arcs that have no effect on the outcome of the story. At a point it gets ridiculous when nearing the end 5 armies battle each other. It completely loses grip of the story and becomes all about the high budget cgi fight scenes. Despite this it still made a killing at the box office likely due to the many hardcore fans of the book and LOTR film series.