The eBooks are typically storybooks for young children. They will need to be downloaded to a tablet or phone in the "READ" format for the narration part to work. Some computer browsers are also compatible (Chrome, Safari, IE11).
After checking out an eBook with embedded narration, select the "READ" format.
The eBook will load in the browser. Click the "Start Narration" and the pages will turn automatically to keep up with the narrator.
Without showing too much of the page (I don't want any copyright infringements!), see how the word being read turns red?
The narration can be paused and resumed at any point.
I should note that I had trouble downloading this eBook for offline reading. I'm investigating the issue and will post any new information when I get it. For more information on the READ format with narration, check out this help article.