Aha moment for me about free time being a network good. The issue is that free time is valuable mostly because you get to spend it with other people, most of whom work standard business hours. Just having a lot of free time with no one to do things with turns out to be socially isolating and a bummer -- which is why retired people and entrepreneurs who sell their companies for a billion dollars rarely turn out as happy as you'd think they might be.

What makes people happy is PERCEPTION that they have free time.

But actually having free time makes many people miserable, because as Joyce says, it can be isolating. 

free time is necessary for reading? 

Reading time is not free time. It's READING time. :)

what is free time then? I do agree that more happiness is achieved when having free time with friends.

"Time for hobbies" : https://en.wikipedia.org/wiki/Leisure

So I stand corrected because reading is certainly a hobby.