Wolverine's death in the comics was a result of a combination of factors. There was a powerful enemy, and also internal conflicts within the comic's universe that contributed to his demise.
In the 'Death of Wolverine Graphic Novel', apart from Wolverine himself, there were several key characters. One was Dr. Cornelius, who was involved in the events leading up to Wolverine's death. His actions and motives were central to the plot. Then there was the character of Mystique. She has always had her own agenda and her role in this story was to manipulate the situation to her advantage. Also, characters like Cyclops, although not as central as some others, still had their reactions and interactions related to Wolverine's death which were important in showing how the X - Men as a whole were affected by this major event.
Wolverine comics can have value. If they are in mint condition, feature key story arcs, or are limited editions, they can command high prices among comic enthusiasts and collectors.