From Introduction:
So, now I guess it is time to discus exactly what Liber Magus is? First let us take a look at the name. The word “Liber” has three definitions: Bacchus (god of celebration), free, and book.
“Magus” means either the force of magic, or somebody who practices it. Thus “Liber Magus” could easily be translated as “god of magic or magicians”, “free magicians”, or “book of magic”. So which definition fits, you are wondering?
All of them.
This file contains three sections. One discussing the overall alternate spellcasting system, the “god of magic and magicians”. One for the changes to the core system necessary to make it magic-using characters that utilize these changes, the “free magicians”. One for extra material to add into your game such as spells and prestige classes, the “book of magic”.