The Ryanair website says this:
"The only items permitted to be carried onboard are the following items:
Travel Documents (passport), Keys (but no electrical key fobs), baby food, milk, sanitary items and prescribed medicines (except in liquid form unless verified as authentic) essential for the duration of the flight. "
However, BBC News 24 says that you can also take items purchased after passing Security Control. They've specifically mentioned newspapers, magazines and book as being acceptable items.
Chris