This study wanted to show that reading literary fictions would improve Theory of Mind in contrast with popular fictions.

"Our contention is that literary fiction, which we consider to be both writerly and polyphonic, uniquely engages the psychological processes needed to gain access to characters’ subjective experiences."

Interesting study. Maybe that why we read "hard" literary books while along side with popular easy read.

I don't read Jodi Picoult but she is a popular writer. 

Popular books do not help us because they are written with us readers in mind, and would not challenge to our world view. 

Literature, were usually not driven by popularity, or writers were from another time. So these books might not confirm to our world view.

This is why reading literature is worthwhile. Try it. 

Of course, to keep the book market alive. It is best to read a lot of new writers if you could afford it.