Bella is the daughter of a rich merchant who remarried after her mother died. Saddled with a stepmother who is young, beautiful, and not very good at doing anything, Bella has become the de facto head of the household, keeping the servants in line, doing all the menus and some of the shopping, and making sure her two step-sisters are her friends as well as keeping her new stepmother appreciating rather than resenting her by going through her father's warehouses and gathering up small bits of fabric, lace and other bits for all of them to beautify themselves, but saving the best for her new stepmother.
Bella works hard to prevent becoming the resented normal daughter, and knows that if she didn't take the care she did in catering to the others that they would resent her or turn her into an unwanted workhorse. One of the ways she befriends her stepsisters is to help them sneak out to the local guild ball for some dancing and punch, but making sure they all leave before things get too heated or the hard liquor comes out. But when she leaves the town to visit Granny, the local wisewoman who lives in the woods, her old, normal world is dealt a hard shock.
First, she has a nasty encounter with the local Lord's gamekeeper, who thinks she is a peasant girl trying to poach game from the woods, which is against the law. Bella really starts to get upset with him when he tries to demand a pawing (or worse) for his encountering her in the woods, which is when she unleashes her real name and position on him. He's mildly cowed by her name and position, but it still makes him angry when she treats him coldly. She dismisses him and continues on to Granny's house to ask her advice.
But when she stays a bit longer than she planned for, asking Granny for both advice and for her normal teaching about herbs to be found thereabouts so that Bella can make her own potions and tinctures, she tries to hurry home as night falls and the moon comes out. But as she hurries through the forest, she is attacked by a gigantic wolf who knocks her down and nips her ankle before she can scold it away from her. She somehow manages to make it home, and bathes her wound, hoping that the beast can be found and killed.
Of course, her attack doesn't go without being notice, and before she can properly recover, she is collected by the town guardsman and taken to the castle of Sebastian, the mostly-unseen local Lord. As it turns out, Sebastian is not only the lord of the town and surrounding area, but he is also a werewolf, cursed into a monstrous beastly form during the time of the full moon. But as far as anyone can tell, he's never been bitten by a werewolf, nor done any of the usual sorts of things that would lead to the disease or curse of werewolfism. It is a puzzling case, and this is why he stays on his estate and is never seen.
During his beastly transformations, he is supposed to be locked up in a cage and watched over by Eric, his woodsman, and as it turns out, his half-brother. But somehow, last night he broke free of the room he was supposed to be locked in and ran off into the woods, where he attacked Bella. Since no one knows if his disease is catching, Bella must be imprisoned with him for at least three months, since, if she is going to become a werewolf, it will happen in that time.
Bella is upset, to say the least, with her own imprisonment, but she wouldn't want to endanger her father or her own family if she was somehow infected with vampirism, so she agrees to stay in the castle with Sebastian and Eric and wait and see if the curse strikes her as well. But her hunger to see her own family lead to several gifts from Elena, the grandmother who is overseeing the problem of Sebastian's curse- a mirror that will allow her to watch her family, and an enchanted box that will allow her to exchange messages with her father once a day.
The mansion she is now living in is devoid of human servants, but strange, invisible spirits watch over the castle, cleaning where it is needed, cooking food and doing many of the chores that humans would normally do. But Bella is the first person to actually talk to them, and discovers that they aren't merely dumb spirits. Some of them can actually think.
As she sets the castle in order, she finds herself coming to appreciate Sebastian more and more, as well as helping him work on his magic and developing her own magic, which has increased with the trials she has undergone. But as she deals with the trials ahead of her, she must also discover who is behind turning Sebastian into a werewolf, and her fears that she herself might turn fuzzy on the nights of the full moon. But can she discover who is behind the curse when even the Grandmother Elena cannot, and will she be drawn to the bookish Sebastian, or his half-brother and gamekeeper, Eric?
Of course, this book is based on the faerie tale, "Beauty and the Beast". But, unlike the original tale, the Beast is only a beast part of the time- at the full moon. The rest of the time, he's a somewhat bookish mage who spends more time in his head and on his magic than thinking about other people. It takes Bella (whose full name is Isabella) to make him take an interest in the world around him.
Sebastian has to learn to interact with people, and Isabella has to learn to let go a little and not try to run everything around her, and both have to deal with treachery and betrayal and learn to love. And save both Sebastian and Bella when the true author of the curse reveals themselves. But can they do it alone, or will they need help?
Anyone who knows the fairytale will probably be able to figure out who the villain of the piece is long before the end, but the story is very well-told, with lots of twists and turns, and the usual reaction towards people learning about the traditions when they didn't before (cue "Oh, that's horrible- but it explains so much). I enjoyed this book a lot. Even though it's based on a fairytale, the characters are well-developed and never feel like cardboard cutouts. Highly recommended.