I have the same problem. I tried two clip on book lights. The first, had a screw in bulb, wasn't real bright, and required 4 C batteries. The second used a minimag style bulb, and took 4 AA's - it was very bright, almost two bright, but the batteries were part of the unit which made it heavy.
The PT Aurora works great, is light, has long batt life (so far) and the flicker on low mode isn't noticeable to me - I can't see it. It's just enough light to see the whole book, with little left over. It also works with papers, magazines, and other things the clip-on lights won't clip on to. Another plus is that when you look away from the book, say, to take a drink or get a kleenex or something, the light goes with you.
My favorite, though, is putting the book in e-book format on my Sony T665 palm - great screen, auto scroll, built in dictionary, and, of course, the backlight.