A luminous source (10) for reading material includes a light source (20), a light guide plate (40), and a frame (60). The light guide plate is adjacent the light source, and converts divergent light beams received from the light source into substantially parallel light beams emitting from a main surface (42) of the light guide plate. The frame defines a support space (62) and has a switch (61). The light guide plate and the light source are secured in the support space. The switch electrically connects with the light source and controls switching of the light source on and off. The parallel light beams illuminate a page of the reading material from underneath the page.