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. Ginder, 39, says. "There was so much guilt associated with quitting, but when I finally did it, it was liberating."

In the age of the e-reader, dropping a book has never been easier: It doesn't even require getting up to grab another off the shelf. But choosing to terminate a relationship with a book prematurely remains strangely agonizing, a decision fraught with guilt.

"It goes against how we're built," says Matthew Wilhelm, a clinical psychologist with Kaiser Permanente in Union City, Calif. "There is a tendency for us to perceive objects as 'finished' or 'whole' even though they may not be. This motivation is very powerful and helps to explain anxiety around unfinished activities."

The idea of stopping midway is stressful, but still, we do it. And even brag about it. Goodreads, an online community of readers that was recently bought by Amazon.com Inc., allows its 18 million members to rank the most initiated but unfinished books of all time; 7,300 members have voted. Top of the list: "Catch 22," Joseph Heller's American classic. Books in the "Lord of the Rings" series finished a close second.