I want to love this but it's annoying to use and very buggy. The highlighting and auto scrolling is nice when it's working. You can't easily start at a spot on the page and have it keep reading. if you select an area...that's all it will read until you reset it and select another area. The bugs make it unusable though. It tries to read two sections at a time alternating sentences between where you've advanced to and...somewhere else. On a site I'm using for school, it finds the first page in a chapter (not the one I'm on) and starts reading that. I don't know where it pulls the info from but it's really bizarre.

I totally recommend it, very useful when you want to enjoy a long read

This addon does what is advertised, and does it well.
However, I had to remove it. I suspect the functionality that discards irrelevant content is to blame:

When using Wikipedia, >any< article on Wikipedia, the Table of Contents would appear only so long as the page is still loading. The moment it's done loading, the Table of Contents disappears, the article is displayed as though it had never been there.

Since Wikipedia is one of my most frequently used bits of internet, this made Pericles worthless for me.

I originally encountered the problem in Waterfox 56.2.5, BUT it replicates perfectly in Firefox 64.0. That is to say, tables of contents on Wikipedia disappear in Firefox when Pericles is installed, too.

Two stars, because it does the text-to-speech well, but no more than two because it does not handle recognizing irrelevant content well.