Robert Jordan writes like no other. Simple as that.
In The Fires of Heaven, Rand al'Thor leads the Aiel out of the Three-fold land on a quest to unite the world before Tarmon Gaidon, the last battle. Nynaeve al'Meara continues her search for the Forsaken Moghedien, while the other Forsaken plot and scheme to bring about the death of the Dragon Reborn...
The story moves along at a much slower pace than the preceding instalments, switching from plot-based to character-based. Jordan allows each character to flow unchecked in an engaging, fast-moving plotline.
Other readers might find this change boring, as the detailing of events becomes even more intricate, to the detriment of the plot itself. Every single thing is described vividly. It's like the author suddenly decides to allow his readers to enjoy something other than the story.
The author's writing style changes dramatically in The Fires of Heaven. He seems to give his characters too much leeway, but rather than being boring, the effect is even more exciting, given its uniqueness.
In The Fires of Heaven, the characters in the series finally begin to come into their own, as the author tries and succeeds in bringing the characters to life in the minds of his readers. I've actually started having dreams about the books!