@jimmi A plugin would only have a tiny fraction of the features and probably look like crap without a lot of custom CSS applied to the chosen theme. Which most people are simply incapable of. They struggle to make their sites look good as is. A theme is the better choice as it allows full control over the frontend. Fictioneer has been developed primarily for single authors; you cannot expect a writer to be knowledgable about CSS, HTML, and PHP to make this work. Heck, they can barely google "how to create a page in WordPress".
There actually is a plugin that attempted just that: Writeshare. It has not been updated in six years and I just helped a community move away from it. The implementation of book features using taxonomies was questionable imho.
Writeshare is the worst. I tried it and I didn't like it. I think fictioneer has promise. It was easy to use and install with tons of options.
