The books revolve around the adventures of the eponymous Spike and Suzy, two children (pre-adolescent or adolescent depending on the album), along with their friends and family. The stories combine elements of comedy, fantasy and science fiction, such as talking animals, time travel and ghosts. The strip still runs daily in De Standaard, and new books continue to be published: as of 2008, 300 books have been published. While they remain popular among readers from the Netherlands, their popularity in Belgium has plummeted since the mid-1990s.