I bought this for my Kindle e-reader. As you might know the Kindle has no back-light so getting a book light is important if you want to read your Kindle in low light, or dark situations.
This is the book light I bought. It has a bulky clip-on which is the only feature I don't like. It is marketed as Kindle compatible but it takes up a part of your screen due to the clip's bulkiness. The light itself is very powerful, I'm not sure how long the batteries will last. The light is very white and something more incandescent would be easier on the eyes. It takes 3 AAA batteries which are not included, so think of the cost of that when ordering.
The flexible arm that the light on is great... you can twist this light to your preferred position.
Again, the biggest flaw is the clip, it knocks off easily and it's bulky and obscures the screen.
I would not want to use this with a regular book. It is somewhat heavy for a book light.
One last thought, I bought the white one... if it's for a Kindle, like mine was, I'd prefer to get a black one.