Until very recently, Michelle Ginder, a transportation planner in Seattle, forced herself to finish every book she cracked open. An avid reader, she says she felt "like a quitter" for giving up a novel halfway. Then, while plodding through John Sayles's 2011 "A Moment in the Sun" and "still not knowing what it was about," she made a conscious decision to put down the book. She moved on to something more gripping, reading the "Game of Thrones" series.

"It felt so good," Ms....