After being betrayed on a mission in North Korea, Bond is captured, held prisoner and tortured for 14 months. Upon his release he finds himself on the outs with M and MI6, escapes from a military hospital and begins his search for the person who set him up. This search brings Bond face to face with Gustav Graves, a billionaire diamond tycoon who is actually his old nemesis in disguise, Graves' henchman Zao, the NSA agent and Bond girl Jinx and MI6 agent Miranda Frost. Graves has created a satellite laser that harnesses the sun's power in an attempt to clear all mines between North and South Korea in order to ultimately have North Korea become the world's foremost superpower.
Raymond Benson either had an early version of the script or he took some creative liberties because many parts of the Die Another Day novelization are different from the film. None of the changes are major; rather, they are small details such as Bond not hanging onto the bell at the end of the pre-title sequence or the military hospital Bond is taken to being in Seoul, Korea instead of Hong Kong. These differences do not effect the story in any way, but they are noticeable for those who have seen the movie a few times.
Perhaps the best addition to the story was the chapter Benson spent detailing Moon's survival, surgery and rise to power. It also deals with Moon and Miranda Frost's friendship from their Harvard days together through her betrayal of Bond in North Korea. This simple chapter offers more insight into their characters than the entire film did, although if it were translated to the big screen it probably would have slowed down the movie too much for the non-hardcore Bond fans.
Other than the minor changes and the aforementioned chapter, the novelization stays relativly true to the film. Jinx's character is played down to a more traditional Bond girl with Bond doing many of the things she does in the film such as cutting off Mr. Kil's arm with the laser. On the subject of Kil, both he and Vlad have greater character development in the novel.
As a whole, the Die Another Day novel is better than the movie itself. Granted the book reads like a screenplay, but the additions and extensions make it a more thorough story and, as a whole, more interesting. The novel is a fast read; I tore through it in about 5 hours, but that's also because I knew the story before opening the cover.