There is no special food required to prepare for reading. Unless you have some particular physical disorder, you should eat a diet rich in fruits and vegetables, low in saturated fat and meat, and you should start your day with a good breakfast. Don't overeat and get plenty of fiber in your diet. Check the link below for recommendations. Good luck!
Michael Bentley, Expert Panel Member
While there isn't a specific food that you can eat to improve your ability to read (or it hasn't been discovered yet), you can eat foods that will help you improve your concentration. Caffeine and sugar, in moderate doses, will improve your ability to focus.
This assumes that you have a healthy diet, aren't skipping meals, and are drinking enough water. The side-effects from not following those guidelines will far outweigh any benefits from focus-improving foods.