Queen of Glass is the original draft of Throne of Glass, written by Sarah J. Maas under the pename S. J. Maas. It was uploaded to FictionPress in 2003 and became one of the most popular stories on the site. 
In December 2008, Sarah removed the story from FictionPress with aims to get the book published.  Sarah then rewrote the entire book, and published it in 2012 with Bloomsbury Publishing, under the name, 'Throne of Glass'.
The story was divided into three parts, which was later adapted into the first four books of the series.