Don't do that. You will get a LOT more than the backstory. You will also get huge spoilers about future developments about all of the characters. You want these things to be surprises. I'm willing to discuss future story behind spoiler tags and past story as it differs from the books, but I wouldn't want you to ruin the entire show by reading the wiki on characters.
I've heard that they are pretty good. The narrator who did the first three wasn't available for A Feast for Crows so it was someone different. They've recut it with him again because of fan complaints.