This is a really lovely & useful little book light. The fact that you can just whip it off and use it as a bookmark is really great! I can't comment on battery life, as I haven't had it long enough yet. It is bright enough to read by, without disturbing anyone else. The only very small quibble I have with it, is that the cut-out where you fix it onto your book could be a little longer to help give it a bit more stability.