This paragraph here, from your article sure does sound as if medium wants to get in to the publishing world--Not just selling books:

“We’re impressed not only by Glose’s reading products and technology, but also by their experience in partnering with book authors and publishers,” said Ev Williams, Medium CEO. “Books are a means of exploring an idea, a way to go deeper. The vast majority of the world’s ideas are stored in books and journals, yet are hardly searchable nor shareable. With Glose, we want to improve that experience within Medium’s large network of engaged readers and writers. We look forward to working with the Glose team on partnering with publishers to help authors reach more readers.”