This is really exciting to me, and I'm glad to see a new review. I was introduced to open-endedness as a motivator for interesting behavior by this Ted talk: https://www.ted.com/talks/alex_wissner_gross_a_new_equation_...

Edit: Adding relevant phrases, oddly absent from the O'Reilly article.

The Equation for Intelligence F = T ∇ Sτ

"Intelligence is a physical process that resists future confinement."