I actually implemented something like this for my ownself. I have a suggestion that you may want to try out as an experiment. Somehow give the user the ability to choose when to receive the next update (and maybe even how much). So for example I know I'm going to be busy the next couple of days but I want to keep the continuity, so maybe I can schedule to have only a couple of paragraphs sent to me. Or I know I'm going to be bored out of my mind this weekend I can schedule a page sent to me every 4 hours.

In other words if you can add this little gamification aspect and the idea that I have or can have more active control over what's delivered to me, I suspect you'll have better engagement. For me after the novelty of implementing my own a-page-a-day solution wore off and when I missed a few days then it just seemed like a chore to catch up with my missed reading.