Does the plate really stay between the books without falling?
Yes. The plate is thin but sturdy, and once it's slid between two books that sit flush on the shelf, the weight of the books holds it firmly. It won't shift with normal use.
How long do the batteries last?
On regular evening use of a few hours a night, the button batteries last several weeks before needing a swap. They're widely available and easy to replace.
Is the light bright enough to actually notice?
It's designed as an ambient glow, not a reading light. The soft amber LED is bright enough to catch the eye in a dim or evening-lit room, giving that cozy lantern feel.
Will it fit any bookshelf?
As long as you have two books that sit upright next to each other with a bit of space between them, the plate slides right in. It works on standard shelves, cube shelves, and even between larger hardcovers.