I use these as side-lighting for microscopic inspection of electronic parts. This is excellent because it produces two different levels of lighting due to its containing two LEDs each lamp.  The LEDs consumes low amounts of battery power.  After moderate use I've yet to replace the batteries in my first set that I purchased nearly three years ago.  The base includes a clamp to attach as you please, the neck is flexible to place the light exactly where it's needed.  The product comes with batteries so ready to go upon receipt.  Also there is the option to connect AC power adapter to these book lights although I've never tried it.  I especially liked that these were offered in my favorite color pink.