The Simple Touch uses ONLY reflected light and has no internal light...which is why the battery lasts weeks with the Wi-Fi turned off. However, it is effective with surprisingly little light. My bedroom light is a 20 watt energy efficient bulb that has about the same light output as a traditional 80 watt bulb. That is NOT enough light to read a traditional book without eyestrain. However, I have used that light to read the Nook Simple Touch. I select a larger font than most people use, and with a larger font, the Nook is easy and pleasant to read...with just that 20 watt bulb.