The apps I pay for are simple and focus on a super basic interface. BookFusion and Libro.fm are great examples.

Recursion is not needed when you regress system components to its foundamental representations, which can be derived without any recursion involved. In the thread example, I don't need to recursively determine how to compress how a planet orbits a mass. I only need to 'jump to the end' by define the rules of gravity and the mass/velocity of the bodies. What I'm driving at: I am suspicious of "Recursion is the Key" to better intelligence as it moves the goal post of understanding intelligence to 'mere' reflections without having to address other qualities of representations, qualia, novelty, etc.