Many moons ago, I ran across a recipe for chalkboard paint - could be a cool thing to paint on the cover of an altered book...
Chalkboard Paint:
3 teaspoons acrylic paint [colour of choice]
1 1/2 teaspoons glazing medium [water based]
1/2 teaspoon powder tile grout
Mix all together and blend really well. You should only mix as much as you will need for your project. It doesn't keep well, but can be stored in an air tight container for a few hours. After a longer period of time, the paint will begin to thicken a little and become a bit brittle.