A feature I have found becoming popular on many blogging websites (like Medium for example) is the read length of articles in minutes displayed at the beginning besides the author and date.  It is effective in most situations to make a tedious homework reading seem shorter than you might have thought, but also a good heads up that an article in full might be longer than you have time for.  I find it as a good motivator that an article is of manageable length.  However, the HBR went one step further with an active progress bar that sits at the top of the page and progress like a loading bar as you move down the page.  The only thing is that it is design to measure your position on the entire page, rather than the article text itself, so you end up finishing the read before the progress bar completes.

Sources: https://hbr.org/2017/02/repealing-obamacare-would-be-bad-news-for-the-gig-economy