Final Crisis, IMO, is poorly written and hard to follow without a full understanding of the DCU, and maybe not even then. Some of the tie-in books are a decent read, however. But as an event, particularly one which trumpets itself as the "Final" crisis, it is far from successful thus far.
I want to smash my head into a wall trying to read that -- crap.
I do like Secret Invasion though, a lot of the tie ins have been good for that and you don't need a strong following of the Marvel U to understand what has been going on.