To be fair: it's not an example of particularly good writing. As Roy himself says:

["hypertext as the engine of hypermedia state"*] is fundamental to the goal of removing all coupling aside from the standardized data formats and the initial bookmark URI. My dissertation does not do a good job of explaining that (I had a hard deadline, so an entire chapter on data formats was left unwritten) but it does need to be part of REST when we teach the ideas to others.

https://web.archive.org/web/20080603222738/http://intertwingly.net/blog/2008/03/23/Connecting#c1206306269z

I'm actually surprised that Fielding's dissertation gets cited so often. Fielding and Taylor's "Principled Design of the Modern Web Architecture" is much better.

* sic