When a font-family value is used to refer to a font-family defined within a @font-face { } statement, then the value is NOT a font name but a font-family name. Therefore the font-family name should be in double quotations. In other words, font-family: Georgia is interpreted by the CSS as meaning the Georgia font and will have no effect on the text due to the limitations of Sony's ePub engine (ADE), whereas font-family: "Georgia" is interpreted by the CSS as a name assigned to a font family via an @font-face { } statement.

CSS files are read and interpreted in sequential order from beginning to end. In other words, you must first define something in CSS before you can refer to it. So @font-face { } needs to precede (be defined prior to) any subsequent references to it.