Winter's Passage is a free novella from Julie Kagawa. It's only available as an eBook and I suggest downloading it here.
The Iron King is the first in the Iron Fey series. It's fantastic!
I highly recommend it to faerie lovers everywhere.
It takes place after The Iron King so you probably shouldn't read it until you read The Iron King.
The next novel in the series is The Iron Daughter which will be released August of this year! :D