It even has rules for things like daily weather, which I tend to forget to include. There's lots of help for quickly creating NPCs. It covers both long-term arc plotting as well as improvisation. It has numerous plot prompts and story hooks, as well as means for investing both characters and players (or in my case, readers) into the adventure. It has extended lessons and quick tips for writing plots and handling multiple characters. It is particularly useful because D&D is the root of my favored genre.
For me, at least, it does double duty as one of those how-to-write books. In addition for its stated purpose, the game itself, I find it is also tremendously helpful in for novel writing as well.
I finished reading the Dungeon's Master Manual for D&D e3.5 recently.
