To write a good novel in Sims 2, first your Sim needs to be literate enough. This means having a decent writing skill level. Then, think about the theme of the novel. Is it going to be a comedy, a tragedy or something else? Once you have the theme, start creating the characters. Give them unique personalities and backstories. After that, your Sim can start writing the story, following a logical plotline. They should also pay attention to details like descriptions of the setting and the characters' emotions. Revision is also important as the Sim's writing skill improves over time.
In Sims 2, for writing a great novel, start by ensuring your Sim has a proper writing environment. A quiet and comfortable space can enhance their focus. Then, build their writing skills through practice. As they write, encourage them to explore different genres. If they are more into romance, start with a love - based story. For a mystery, create some suspenseful elements. Also, make sure your Sim interacts with other Sims to gather different perspectives which can be used in the novel.