Lirael is a Daughter of the Clayr, but she lacks the Sight which characterises her people. She finds consolation (and a friend, in the form of the Disreputable Dog) in the Great Library of the Clayr, but when the plots of a powerful necromancer threaten the safety of the Old Kingdom, she must leave her sanctuary and try her best to protect the living from the Dead.
I liked this book very much - especially the sections set in the Library, which is a wonderful and mysterious place. I didn't warm to Prince Sameth as much as I did to Lirael - I felt he was too whiny. That's probably rather unfair, as it seems to be part of his journey to overcome that, but I couldn't like him much. Also, I suspect that I rather resented the sections of the book devoted to him, because I wanted to get back to Lirael and the Dog.
That aside, I enjoyed the book immensely and next time I'm buying new books, a copy of Abhorsen, the next book in the series will be at the top of my list.