Prior to Acrobat 1.0, there were no general eBook readers that weren't proprietary. The most pervasive DOS book reader from the early 80's - before Windows and faster machines - was IBM BookManager. BookManager was used mostly by fortune 500 companies that bought and used IBM and competitor products; IBM produced millions of pages of product doc written using Generalized Markup Language (GML), which was very popular back then, and is the foundation of SGML, HTML, and XML. (many don't know the the GML acronym is also the first letter of the last names of the three men that invented machine-independent semantic markup - Goldfarb, Mosher, and Laurie). It surprises many that BookManager is still in active use today (there were also subsequent Windows and mainframe editions), thought its use is finally fading. ePub is making inroads because it is accessible and device scalable, but PDF isn't going away any time soon. I know all this because I worked on developing hypertext BookManager extensions back in the mid-80's, and, I hold the first-ever published invention disclosure in the US Patent Office that enabled audio and video to be included in hypertext browsers driven by structured markup (which, had it been a patent and not a publish, would have made a lot of news when video and audio on the web emerged several years later) - but at least it prevented anyone else from getting a patent on HTML launching rich media as a result.
In theory, it would be fairly easy to convert HTML to GML then use BookManager/DOS or BookManager/Windows to render it. There are still copies of the GML program that IBM made a commercial PC/DOS product called SCRIPT/PC available on eBay, which was a knock-off of IBM BookMaster used on IBM mainframes for decades. I still run BookManager Read/DOS on my 5160 PC/XT, but you'd also need BookManager Build/DOS to create the readable books.
Regards,
Mike
