I think it would benefit the readability of CHYOA.com to implement options for text display. The colour options (Standard white, sepia and dark) are already implemented. But I think compared to books the text on CHYOA is extremely wide. I realise everyone has their preferences for how many characters/words should fit in one line. Some browsers include a reading mode, where text width and size can be altered. Of course, using those modes on CHYOA disables the links at the bottom and the side bar. Now, my suggestion would be to implement buttons to change font size and text width into the menu for colour options already present. It would be similar to reading mode but of course without cutting away all the rest of the content. Here is the options menu in Firefox’s reading mode as an example:
There are browser extensions which allow you to overwrite a website's CSS. (On Chrome I use the extension Stylebot for that purpose.) You can use such an extension to change the font or size of a specific element. e.g. Code: div.chapter-content { font-size:25px; font-family:arial; } (Stylebot also has a basic styling option where you wouldn't need knowledge about CSS.) This is kind of a workaround, though you only have to do it once to have the same style every time you visit the site.