I love books, which is why I wanted a Kindle. Our house is full of books, some shelves double-stacked, so the thought of being able thousands of books to my library without the house collapsing under the weight was very appealing.
Having got the Kindle, I could then see the need for a case, to provide it with some protection when I was carrying it around. But I wanted a simple case, rather than one with an integral light. So we added this light at a later stage, to allow reading in a darker room.
It does what is needed, providing sufficient illumination for the screen's passive display (or, for that matter, a regular book) to be readable in a dark room, without flooding light all around. I'm fairly sure that as a general-purpose clip on light, it would also do a good job.