Why do you do recovery rides indoors? I do a lot of training on my test bike, but I only do very specific high intensity interval training because of the benefits of a controlled environment. Recovery rides doesn't need this, and they are generally quite nice breaks from the intense training, so I always do these outside. Also, riding anything but hard indoors is so boring no distraction is enough
But to get back to the main issue, I go through a lot of TV programmes when training. Right now I'm watching Babylon 5, which seems to go on forever. Usually not a fan of SF, but this works although it's a bit silly sometimes
Anything with a lot of action seems to work fine for me. I guess what doesn't make you bored to death is quite individual as well.