Bennett book test by Nils Bennett
A novel idea for the book test:
You get a thick book, which has a hard cover and a bookmark. The viewer can insert the bookmark himself anywhere and it will later end up exactly on the page you know - a clever gimmick namely relocates the bookmark!
No matter where the viewer puts it, it ends up being where you want it.
You get the specially prepared book (they are any used book titles from literature, which makes the whole thing unobtrusive).
There is also a detailed German manual.