This is an excellent book, set about 18 years after Sabriel. But, we see through the mixing of the Charter Bloodlines, the emergence of a few previously unknown types of people, rather than the usual Royals, Abhorsen, and the Clayr.
Firstly, we see a Remembrancer. In the book it tells of the fact that the Remembrancer can only be born of a child of Abhorsen and a Clayr. They have the unique ability to See the past, while Clayr only See the Future, (or possible Futures). But the Remembrancer will never be fully accepted as a Clayr, because she won't ever see the Future. Lirael, the title character in this book, finds out she's a Remembrancer, the first in about 500 years, after most knowledge of this art is lost.
Lastly, there is the reemergence of a Wallmaker. Sameth, royal Prince, has always been good with tinkering. But, will the Bloodline continue? This is a rather good question, and no one will know for sure, (except Garth Nix, of cource!!!). This may have come about by the mixing of the Royal and Abhorsen blood, but is this a freak occurrence, or will the Bloodline of Sameth be Wallmakers? Who knows? Maybe we will find out in Garth Nix's forthcoming book, the sequel to Abhorsen, Clariel. To find out more about this, read Lirael, and it's continuation, Abhorsen.
May the Charter be with you!