I read Seth's latest book(let), The Dip, last week. My quick takeaway...if you're not obsessed with what you are doing, you might seriously consider quitting, and move on to something else, something that really sets your hair on fire.
It's an easy read. And while it doesn't offer any instructions or specific decision making tools about whether to quit or not, it doesn't need to...it's simply meant to get you thinking. It's worth an hour or two of your time.