Web reader font/theme settings don't carry over to other books, and highlight color has no "set as default"

I set the font, page color and highlight color in the web reader, but the next book I open is back to the stock appearance. I found three-dot menus next to Theme and Fonts but not next to Highlight color, and once I use "set as default" the dots vanish from that setting too.

Resolution: This is working as designed: web reader settings are per book, and each one falls back to a global default until you change it for that book. To make a value apply to every book, open the three-dot menu next to that setting and choose the option to set it as the default — the dots then disappear because the current value already is the default and there is nothing left to do. Note that "set as default" only changes the global fallback: books where you had already overridden the setting keep their own value, so a book you previously set to a green highlight stays green after you default everything to blue. Highlight color genuinely has no three-dot menu at the moment, which is a gap rather than intended behavior, so it cannot be defaulted yet. A future web reader iteration is planned to invert this and make settings global by default.