http://www.imperial-library.info/

is all the content from this site from the books in the games themselfs?

or is it just a load of fan fiction?

There are a few pieces of unofficial lore released by various developers and former developers but by in large the Imperial Library's collection is taken straight from the games themselves.

There are also a few developer interviews, including a small one with Greg Keyes, and several compendiums of plain-speak information taken from the books.