Just bought a copy of E. J. Mcinnerney's textbook Computational Explorations in Magnetron Sputtering. However, when I download and try Chap2.nb from:

http://www.computationalexplorations.com/mathematica-code.html

I get the following error in Mathematica 10.0.2:

The specified setting for the option FontSize cannot be used.

Can someone point out what is wrong and how to fix it?

Removing the Mediumoption from BaseStyle fixes your problem.