We tested many book lights before and we think this may be the best one we've tried.
This one is sturdy but light enough to not bend a book, it has two levels of brightness, a flexible goose neck so it can shine in any direction and best of all it can be recharged in any USB port. (no more having to get tiny batteries for these little lights)
There are up to 16 hours of light in every charge.
It comes with a charge cable included.
It's a great travel gift and at home can stop all sorts of nighttime arguments if one person wants to read and the other one wants to sleep!