Fairy lights, micro LEDS, or whatever you call strings of small lights. They provide enough light for someone to be up and someone to be asleep. Many are battery powered. Get the rechargeable batteries!
A solar light (LUCI) good flashlight/lantern (Eddie Bauer) for when the power does go out. My DS ended up with several friends studying in his room since he had both going when the power went out the night before an exam.