It runs on 2 AA batteries and will last a LONG time (> 15 hours so far!!). It only draws .3 amps at 3 volts, so it's quite miserly. There is a small round button that "clicks on and clicks off" the light when pressed. It's located on the base where the gooseneck, fully adjustable stalk comes out. The clip has silicone rubber "grippers" that open wide enough to accommodate most places you'll want to use it. It hasn't scratched nor marred any surfaces I have tried it on. It weighs almost nothing, so it doesn't shift during travel. The gooseneck lets me point it any which way. It's metal, so it stays where it's put.
The best thing about this little light? The output is soft and pleasing. More of a bright glow than a harsh light. It's somewhat directional, but covers a wide arc. I tried it out for reading and it didn't seem to cause any eyestrain. Contrast on the page was good. At distances greater than about 2 feet, the light drops off sharply. It could probably be used to see where you are putting your feet on those late night trips to the bathroom. Of course that would depend on where you clipped it on.
I like devices that just do what they are supposed to (and more!) without any fuss. This is one of those things. I'm a bit sad I didn't think to buy more of them! They come in Ivory and Black and were $3.99. Pretty good deal for something so useful.
Be Seeing You...Down The Road,
Rich "The Wanderman"