Fascinating! As a person who hates spoilers but will still read/watch something even though it's been thoroughly 'spoiled' I found this to be somewhat true. But this still doesn't mean that you should go around telling everyone and their cat how the book series that they currently reading will end.
"Many people live in fear of being "spoiled" for a story by finding out the ending. But a new study by psychologists shows that people wound up liking stories better if they'd been told spoilers in advance.
UC San Diego psychology researchers Nicholas Christenfeld and Jonathan Leavitt wanted to know whether it was true that spoilers actually ruin people's enjoyment of stories. They decided to find out, by spoiling a group of 30 people who were about to read three different stories."