I don't know if it's been mentioned, and we have obviously "trended" this direction... But I think it's worth stating really explicitly.
Whatever you choose...
Get an LED Light!
LEDs have improved massively, and their battery life is
very long. It's either comparable with my Reader or longer in terms of life... meaning about 2 weeks at the rate I read -- and I do the
majority of my reading at night.
I had the incandescent Itty Bitty Book Light, which required 2 C-Cell batteries (heavy!), and lasted about 1/2 to 1/4 the time. Compare 2 weeks or more with AAA Cell, and there's another major advantage: weight.
Incandescent bulbs are white, which is their biggest advtantage. But the battery life/cost is just not worth it. And the famously blue-tinge of LED approaches white quite well, though that depends on the light, as you can see from the first post.
I consider this the single most important feature in any Light.
LED! There you go!
-Pie