Happy to see this officially released 
Is it possible to match the fonts in reader mode to the font-list of the platform? For example, we’re using Open Sans, but that’s not an option on the font dropdown for Reader Mode. Would be a nice touch to have the same list of fonts to choose from.
Edit: I’m also noticing that topics which use Discourse TOC, but do not have a reply are not showing the Reader Mode Icon.
You can see an example here:
However as soon as there is at least one reply, the Timeline, ToC and Reader Mode seem to appear as expected.