First of al let me thank Amazon for its service. I received a defective item (light was not recharging), and I got a replacement very soon. I also got back the charges for shipping back the defective item. Note that I live outside UK, so this was not too obvious.
Let me get to the light now. This is a perfect addition to the kindle (even in colour, if you have the graphite one), expecially if you have the habits of reading in bed. It is lightweight, so your arm does not get tired, and the orientable stem permits to direct the light in order to avoid reflexes on the surface of the kindle. The battery charge seems to last a lot. After the first charge I have read at least ten hours and I still have no need of recharging it. Of course you may find cheaper items, the price of these lights is a relevant fraction of the price of the kindle itself, but if you read a lot at least you spare the cost of buying new batteries.
Finally note that the light has the same plug for recharging as the kindle tself, so both can be charged in the same ways. In the packaging you wil find a cable which connects to any usb socket for recharging purposes (no firmware updates for the lamp, thank God!).