Graceling was such a fabulous book that I had to look up and see what else she has written... Here is what I found
Fire, Graceling's stand-alone prequel-ish companion book, takes place across the mountains to the east of the seven kingdoms, in a rocky, war-torn land called the Dells.
Beautiful creatures called monsters live in the Dells. Monsters have the shape of normal animals: mountain lions, dragonflies, horses, fish. But the hair or scales or feathers of monsters are gorgeously colored-- fuchsia, turquoise, sparkly bronze, iridescent green-- and their minds have the power to control the minds of humans.
Seventeen-year-old Fire is the last remaining human-shaped monster in the Dells. Gorgeously monstrous in body and mind but with a human appreciation of right and wrong, she is hated and mistrusted by just about everyone, and this book is her story.
Wondering what makes it a companion book/prequel? Fire takes place 30-some years before Graceling and has one cross-over character with Graceling, a small boy with strange two-colored eyes who comes from no-one-knows-where, and who has a peculiar ability that Graceling readers will find familiar and disturbing...
AND(it says book three, so I am slightly confused...)
Book 3, tentatively titled Bitterblue and currently in progress, is a companion book to both Graceling and Fire and takes place in the seven kingdoms six years after Graceling. As you may have gathered, the protagonist is Bitterblue. Yes, Katsa, Po, and others from Graceling whom I'm not yet willing to name do appear in the book. I don't know yet when it'll be coming out, and heartily invite you not to ask ^_^. That's all I can say about it at this point.