One thing that I recall reading (but can't find now) is that people are statistically significantly likely to finish books with shorter chapters. It just makes so much sense to me - I want a feeling of accomplishment as I go through the content, with clear stopping points, making it easy to keep going, and also easy to pick up again.

My favorite in this regard is Minsky's "Society of Mind" where essentially every chapter/mini-essay is one page, a form which he argued is a good fit for our mental processes.