The human brain is not very good in picking up the word ‘no’, so this could better be displayed with a prohibition sign (where the picture speaks for itself). I would also suggest displaying all areas where laptops are allowed, to get a higher awareness about rules surrounding laptop use. People in general do not like to hear what they cannot do: it takes away the feeling of freedom and causes resistance. Explaining where they can use their laptop will help diminish this feeling.There are two more reasons to choose a picture or pictogram. First of all the library has many international visitors, and the current texts are mainly in Dutch. Therefore an image that will appeal to everyone is perfect too. Secondly, the library is currently full of how-to texts and information that mostly is totally irrelevant to visitors. Putting up another text will therefore be completely useless, since nobody reads those texts.
A totally different option would be to diminish the quality of the Wi-Fi in the reading room (in this room they already left out the sockets). Most people that are using laptops or other electronic devices are using internet. Making this room less attractive for laptop users – without telling them they are not allowed to use their laptop – will help diminish the amount laptop-users.