The Filth begins by showing the reader a typical day in the life of a man named Greg Feely. He goes to work, rides the bus home, looks at pornography and feeds his cat. He's about to go to bed when he discovers a strange woman in his shower. She tells him that his real name is Ned Slade, and that he is actually a secret agent of The Hand, a shadowy organization that keeps the world safe from various surreal events that would disrupt the status quo. Over the course of the book, he sees other dimensions, meets cyborg dolphins and chimpanzee snipers, and fights insane superheroes, rogue agents of the Hand, and pornographers who want to destroy the world. At the end of the day, though, all he wants is to get back to his life as Greg Feely.
I will warn you: this book is not for everybody. It is full of some truly disturbing images, and despite the bright colors and fast pace, is actually rather dour and melancholy. However, if you can handle a grim, twisted tale that is unlike anything you have ever seen (or probably ever will see), then you should pick this up as soon as possible.
EDIT: If you do read this book, and you STILL have questions (and you will), this site will have answers.
Recommended for: Fans of David Lynch and/or Charlie Kaufman; people who have taken hallucinogens; people going through a rough period in their life.
Not Recommended for: people who are ON hallucinogens; people who are fully comfortable with their perception of reality.