Have purchased loads of clip on lights in the past, only to consign them to to the bits and bobs draw as they never really delivered.
This product, on the other hand, delivers and delivers well. The option of having one or two lights on is great (with one light providing loads of illumination) and the ability to purchase the optional AC adapter is a nice bonus.
Not only have I used this with my Kindle DX (there's padding on the inside of both parts of the clip to prevent marking and scratching), I've also used it as a standalone "desk" lamp next to my laptop with excellent results.
I don't think I'll ever need to try another booklight again - this one really is fantastic. As another reviewer has suggested, I'd highly recommend buying the optional adapter - it really does extend the functionality of the light.