Slawter is the third book in The Demonata series (4th chronologically) written by Darren Shan. Even though all the Demonata books can be read separately this book follows on from the 1st in the series, Lord Loss and the 2nd in the series, Demon Thief. The protagonist is Grubbs Grady, who was also the protagonist for Lord Loss.
The book is set about a year after Lord Loss takes place. When the story takes place Dervish, who has just returned from his battle with Lord Loss, a horror movie producer named Davida Haym offers Dervish a chance to work on the set of her new movie, "Slawter". He wakes up and finds himself in a small room in one of buildings that make up the town Slawter. Dervish and Bill-E are also in the room with him and he uses special magic to wake them up. The three of them then run into the town trying to warn people to get away by saying there is a gas leak and the town will explode soon. Back at Dervish's house, Dervish tells Grubbs about what his future would be if he did have magic. When Dervish scans Grubbs for magic powers he thinks he has none, but in truth, Grubbs had hid them without knowing. Later he decides to check if he did have powers, and managed to switch the light on and off without using the switch and make his reflection disappear. To have the power to conceal his powers from Dervish and to use magic in the real world away from any demons can only mean one thing— Grubbs is a magician.