Galaxies: An Empire Remembered is a book written by James M. Crosby which told SWG’s history in great detail, and is considered as a great source of information for those who were looking to know more about it. Unfortunately for some time the book was delisted and has become hard to find, but not anymore, it has been announced that it will be getting a reprint sometime in December 2021. For more details please visit MMOFolklorist.
Update December 2021:
Amazon link for the hardbook