Book 2 was really a transition point in the series. Throughout all of Book 1(which I still adore), the plot was Aang had to learn all four elements to defeat Fire Lord Ozai.
Book 1 had a much simpler plot and build-up than the other Book 2 because:
A) This distance between the North and South Pole was much farther than the distance the Gaang had to travel in the Earth Kingdom. Therefore, the Gaang could not spend as much time in one place as they could in Book 2. The was less time to develop an intricate sup-plot(such as the conspiracy in Ba Sing Se). There were 8 episodes in Book 2 where the Gaang was in Ba Sing Se, The Drill through The Crossroads of Destiny. The Gaang never had to travel extremely far distances in Book 2, leaving a chance for several story arcs. In Book 1, the Gaang had to travel across the entire world.
B) In Book 1, the Gaang always had a destination, which was the North Pole. The only place to find a Waterbending master was at the North Pole. For most of the first half of Book 2, the Gaang wasn't going to any specific place (Except Omashu, 201-203). Unlike the Water Tribes, a bending master could be found anywhere in the Earth Kingdom. After Toph joined the group, the Gaang had nowhere to go. The introduction of a new plot mid-season was necessary, unlike in Book 1.
C) The turning point of the series was The Library, where the solar eclipse was discovered. Instead of the plot that Aang had to learn all four elements, it was discovered that there was a "shortcut" to restoring balance. Aang no longer had to learn the elements, all he had to do was show up during the eclipse and take out the Fire Lord while he had no power. This discovery gave the Gaang a place to go, Ba Sing Se, even though it was not that far away(the actually trip to Ba Sing Se only took 3 episodes). Because of the new plot, Book 2 became much more complicated.
D) The Water Tribes were not that important to the war anymore, mainly because it was the smallest group (besides the Air Nomads). The Earth Kingdom, on the other hand, was the largest and held much more importance to the war. A conspiracy in the Earth Kingdom meant a lot considering it was the only wall (no pun intended) between the Fire Nation and victory in the war. Ba Sing Se was more important in terms of size and army than the Northern Water Tribe.
E) Both Book 1 and Book 2 had two kinds of villains: one that is developed over the course of the season, and one that is not really developed. Zuko and Azula were the developed villains of Books 1 and 2, respectively. Zhao and Long Feng were the not really developed villains of Books 1 and 2. Zuko and Azula were both interesting characters in each of their roles in their books. The same can not be said for Zhao and Long Feng, however. Zhao goal was not as interesting as Long Feng's goal. All Zhao wanted to do was kill Zuko and gain infinite fame for himself. Long Feng wanted complete control of Ba Sing Se, and he executed his plan in an interesting way. Plus, Long Feng's "cool" factor was raised by the fact that he had awesome Dai Li agents. Long Feng's character really helped build up the the finale.
These reasons show the fact of why it was nearly impossible for there to be a complicated sub-plot for Book 1, but why it fit well and was necessary in Book 2. Sorry for the long post
Edited on 09/02/2008 7:07am
