Fiction breaks general writing tools, because a novel needs continuity, a cast who stay themselves, and prose that varies. Sudowrite is built for exactly that: it holds your characters, world and outline, then helps at the level writers actually get stuck, expanding a thin scene, describing a room in your own register, or showing you three ways the next beat could go. It is designed to be argued with rather than to write the book.
It will not produce a publishable novel unattended, and anyone expecting that will be disappointed. As a way through the middle of a draft, though, it is the most thoughtful tool in this category, and the one fiction writers keep rather than abandon after a month.