To curse those with prying eyes

By the power of Witches and Mages
By the wisdom of Crones and Sages
By the Moon as it moves through its stages
By Hecate and Her lunar rages
By the Sphinx and for the Ages
I craft a curse upon these pages

Personally I have this written on the first page of my grimoire and it seems to work out, bad luck follows those stupid enough to open it without my permission. I would recommend doing this spell on your book during the dark moon or during Samhain, I also recommend recasting it ever year or so.