I could understand "forcing" you if they money for the book and didn't want it to be wasted.
But even if that's the case, they still should have given you a choice, and something better than lua.
Many people are recommending java or C++. You could learn the basic in standalone programs, then if you want to do something game-related, you could do Minecraft plugins with Java, or I don't know what with C++.
Not that learning Lua is a complete waste though; the hardest part of learning programming is the concepts, once you've got that, learning a new language is pretty much just learning the syntax and a few other things specific to the language.