A vote for fluorescents, but not the general Camping World type. You want Cold Cathode Fluorescent (CCF) fixtures. They operate at a higher voltage but much lower current than compact fluorescent lights like you have in your house. They are instant on, don't put off any significant heat, don't noticeably pulsate and have a very good color, which I find much nicer than all except the most expensive LEDs.
CCF lights are about five times more efficient than incandescent bulbs and about twice as efficient as normal (hot cathode) fluorescent lights. They are actually a significantly more efficient than LED lighting (80 lumens per watt for CCFs versus mid-20s for the most efficent white LEDs), and they're efficient enough that they're not a major draw on a camper's systems.
Taylorbrite (taylorbrite.com) is a major supplier of linear and "reading"-type CCFs, and they're what I have in my Sprinter.