I'm in love with this universe, and especially the way magic is presented in it. It's a really interesting take on it, and I'm surprised that there hasn't been any TV or movie adaptation - or even video games. 
 As for Sabriel herself, she's a great character, with goals and drives and contradictions and... I'm really happy with the way she was written, and it definitely made me want to read more from Garth Nix, starting with the next book of the series - although I'm sad that it won't be from Sabriel's point of view. 
 Also, I couldn't finish this review without mentioning Mogget, another great character who I'm very fond of. I hope we'll see more of him and Sabriel in the future!