Would you say that you really digest the books you listen to like that? It seems difficult to fathom to me. I generally try to use tedious downtime to think through things and solve problems in my head rather than listening to anything, but I've found that I can't even really keep my thoughts straight while walking outside due to watching where I'm going and the large variety of distracting external stimulus. I feel like I would get absolutely nothing out of listening to an audiobook at 2x speed while cycling.