The players companion is going to give the long term Earth Dawn (3rd E) player two things:
Lots of fluff on how to play their characters - with some great ideas on their 'outlook' on the world as well as how to use this to multi-circle and role play this convincingly.
Secondly: The details and talents for circles 9 up to 15. Including talent knacks and all the new talents to go with them. Crunch. Lots of crunch.
There's not a lot outside of the classes in the way of fluff - you'll not be finding any deeply meaningful world information on Barsaive here.
My biggest bugbear on the PDF presented here is that the BOOKMARKS DON'T WORK! And it drives me nuts. For the price paid I specifically get PDF's over hardcopy so I can jump to the sections I need, and this doesn't do that. I would likely give another star if the PDF was simply updated to give us the bookmarks.