The Everbulb is an object in Dirk Gently's Holistic Detective Agency.
The everbulb was a lightbulb that shone when carried in hand. It probably used the electricity present in the human body to power itself.
During the Spring case when visiting the Spring Mansion, Dirk Gently and Farah Black found the everbulb in the basement laboratory along with the map to the Springsborough maze (Map #2). Dirk called the object first a "magic lightbulb", and then named it an "Everbulb".
Dirk carried it with him when he and Todd Brotzman entered the Springsborough maze on the next day. The everbulb's light aided them in making their way through the dark maze. In the maze's lightbulb room, the everbulb had to be inserted into the exit door as a key and door handle to escape the room. They picked up the everbulb afterwards, and carried it on to the end of the maze.