Answer
If the faces of the glass are not parallel, the light that comes out is not parallel to the light that went in.
Work Step by Step
If the faces of the glass ARE parallel, as in a sheet of glass, the light that comes out is parallel to the light that went in, though it is displaced slightly. This is shown in Figure 28.15.
However, if the faces of the glass are NOT parallel, the transmitted light's angle differs from the incident light's angle.
This is discussed on page 525, and an example with a prism is shown in Figure 28.16.