A whole bunch of preview videos (not quite trailers; more like introductions to various families and characters) were released today. I won't list all the links here, but you can find them here
I would comment on the posts about the books, but it's too hard to do so without giving anything away. It's interesting to read the reactions of people who are just reading the books, or have only read one. They are definitely not for everyone, but if you are a fan of fantasy it doesn't get much better, imo.