Despite the title and the subject matter, this is not a dark or depressing book. It is a very quick read (less than 170 pages), and it's quirkiness and irony makes for a very entertaining story.
Set at an undefined period of time in the future in France, we learn that Earth has been ravaged by man's selfishness and greed. Mankind is a depressed race, which means that business is booming at The Suicide Shop. This business has been by the Tuvache family for generations - they sell anything and everything that one might need to commit suicide, including some very clever inventions. The parents, Lucrece and Mishima, are very contented in their misery, and proud of their two eldest children Vincent (named after Van Gogh) and Marilyn (named after Marilyn Monroe). These two youngsters are both incredibly bored of life, and depressed. However, Alan (named after Alan Turing), the youngest son, is a worry to the family. He is full of the joys of life, and has an constant sunny nature. He refuses to buy into his parents' misery, and this worries them. But despite their resistance, Alan is determined to spread the joy...
All the way through this book, I was thinking that it would definitely make a great film, if someone like Tim Burton were to get their hands on it. It's an unusual premise, and is actually a lot of fun, but it definitely has a sting in the tail.
Short enough to read in one sitting, I would definitely recommend this for a lazy afternoon!