Apparently a friend or colleague of hers, who had the manuscript to read, put it online. I doubt it was a publicity stunt, because Meyers says she has put the book on hold "indefinitely" and doesn't think she wants to finish writing it. You can read all about it on her website. She wrote a letter to her fans explaining what had happened, and you can tell she was very upset and angry about the whole thing.
What was her unfinished manuscript doing on the internet in the first place???? Was it really a leak, or could it have been a publicity stunt?
Midnight Sun is the book that began as a writer's exercise for Meyer. She was writing the book "Twilight" from Edward's point of view. Unfortunately, there was an internet leak and someone posted an unedited, unfinished manuscript of the book online. Stephenie Meyer was very upset, understandably, and decided to put the book on hold. However, since she knew people would try to look for the leaked part of the book online, she posted her unfinished manuscript on her site so people could read it.
Meyer's was writing the new book Midnight Sun but it was leaked online and she was angered by that. From that she has stopped writing the book and I do not think she will continue it but there is a chance that the fan may convince her.
Midnight Sun will probably never get published. Since the incident that happened with the manuscript being leaked Stephanie Meyer feels that it's best to not continue to write because if she did she would probably kill off the Cullen family. You can searching for the blog post on her website. However, she did write the Second Life of Bree Tanner which is the companion of Eclipse through the perspective from the newborn vampire girl that was killed by the Volturi in the end.