I love the
Ritelite. It isn't small -- I describe it as the size of a small streetlight -- but it's great. The light bar is roughly 10cm long, with approximately a 20cm stalk that plugs into its battery pack (you can also hook it into any USB port, so it makes a nice laptop light, and I have mine hooked via USB extension cable to a hub right now, so I can use it as a desk light). It has 5 LEDs distributed across that light bar, so it's almost glare-free on my 505. It uses common AAA batteries instead of those spendy lithium button cells, which is one of the main reasons I bought it. I didn't expect it to be quite so big, though!
The own sides are the size, the weight of the AAA batteries, and the fact that the clip on its battery pack is quite sharp; I'd be reluctant to attach it to a case directly. I have an M-Edge Executive case, and I'm going to make a little bracket (just a bent piece of aluminum) that fits into the book light holder on the case that I can clip the book light to.
Anyway, a compact, lightweight book light it's not, but it's so useful, so flexible, so bright, and so glare-free that I wouldn't trade it for any other book light I've seen. Right now, it's rubber-banded to a little tower desk fan, lighting up my whole desk area. It also has a low setting, if you don't need quite so much light! Oh, and there are little blue-tinted "window" spots on the top of it, to provide some ambient light to reduce eyestrain.
Anyway, that's what I have, after a lifetime of all sorts of book lights, and it's the one I'm staying with for the foreseeable future. I love it.