The font changes in the book because they are showing a different area in the book. Most of the time the book follows Ender and this has one set font, the font changes when Colonel Graff and Major Anderson are talking privately. The font also changes when the character is reading or emphasising a piece of text. The font also changes when there is a subheading or a given. The font change is a classic way of highlighting a special or important phrase that is being said the font is changed for this so it catches your attention.
In Enders Game the font changes repeatedly at the beginning of each chapter. The reason for this is because in Enders Game there is a secret plot behind the regular plot of Ender Wiggin. This secret plot follows Major Anderson and Colonel Graff who are watching Ender in the background. The reason for this font change is to show different scenes in the book. Font. change also occurs when someone is emphasising a word or they are referencing someone else.