In as much as reading, watching actual plays, checking out reviews and the like can help you get a glimpse of what a game system is like, you don't really learn the game until you dive in and play it.
Cause that's when you start to see beyond the rules as written, and experience the mood and tone the people playing the game add to the rules on the page. That's when you get a feel whether or not it works well with your group or not. That's when you can say, "This is fantastic!" or "This doesn't work for me."