The first book is called THE GIRL OF FIRE AND THORNS and the second is THE CROWN OF EMBERS. The third book will be called THE BITTER KINGDOM. I just finished reading the second book, and really this is just fantastically engrossing stuff. All of the characters are so well-developed, the lead, Elisa, is wonderfully complex. The love interest -- whom I won't reveal -- is wholeheartedly swoon-worthy. There's action, adventure, a wee bit of humor, intrigue, conspiracy, family.... ah, it's just really glorious.
Highly, highly recommended!
There's also a novella that's a prequel and told from Elisa's sister's point of view called The Shadow Cats. I haven't read it yet because I'm not ready to go backwards and out of Elisa's mindset, but I'm sure it will be fantastic.