In a well written Bookvoid document, the triangle buttons will unveil more information about the subject described in the heading, paragraph or sentence just preceding the button. It should never reveal information about a new subject or a new part of a subject but always a description of the same subject with more detailed descriptions of the parts mentioned in the parent section. Along with the subject and its parts described in more details, sub-sections can include further information about the different kinds, sub categorizations, sub species, notable instances or examples of its parent. Information covering other parts of the subject should be located in sibling sections lower on the page, not in hidden subsections.
This allows readers to choose the learning strategy they prefer. They may read over top level sections in a breadth-first strategy and then come back and drill down into more details for the sections they are interested in. Alternatively, they can use a depth-first strategy and learn everything they need about each part before moving to the next one. The hidden subsections may also include different perspectives or learning tools tailored to different types of readers.
Authors are encouraged to use simpler more familiar language in the top level sections and use more precise and advanced language as the sections get deeper.
It is not a good idea to hide too much. As mentioned previously ( here
), knowledge is sometimes circular in nature and sometimes it builds on top of previous knowledge. In the later case, when a concept is needed to understand something written later, the first concept should have an visible introduction detailed enough to understand what is coming. Otherwise readers might be tempted to skip too much and be confused later.
With Bookvoid books, there is no need for a separate table of content or footnotes. The list of topmost headers with all subsections collapsed is equivalent to a table of content. Inline collapsed sections replace footnotes and "tl;dr" paragraphs precede the collapsed sections they describe. Bookvoid book authors should strive to make their text compatible to both readers who want just the executive summary and those who are interested in the tiniest of details.
There are benefits for authors as well as readers. By structuring books so that they contain information for a wider group of readers, authors no longer need to publish multiple books for each type of readers and readers don't need to seek more advanced books when they feel they have learned the basics. The advanced information can be hidden in subsections inserted seamlessly.