I use an M-Edge e-luminator. I prefer it for a couple reasons, although I liked the 1st generation light better. First, it uses 1 AAA battery, so they are easily replaceable and I can use a rechargeable battery. Second, it doesn't clip to the device or cover, but slides between the nook and cover. Third, it has 3 brightness settings and shuts off automatically after an hour (with a warning first to prevent if necessary.)
The first generation light had a longer neck and was a little more adjustable, but I'm used to the new one now.