Lessons in Execute Program are just a few minutes long. You read a few paragraphs about a new concept, try it out immediately, and repeat a few times to cover some core details about that concept. Then you’re done.
This brevity is possible in part because Execute Program’s lessons assume solid recall of prior material, but I feel the presence of the interactive prompts may be doing more work. The author doesn’t need to spend as much time describing the concept because the reader’s about to experience it for themselves. This relates to a few phenomena I’ve written about:
In this way, the lessons actually feel much like the review sessions: they’re completable in a quick sitting, and they don’t tax your attention span. This similarity is amplified by the similarity between lessons’ and review sessions’ interaction models: Execute Program’s lessons unfurl their prose in response to reader interaction.
See also Incremental reading