Simple puzzle.

Ok, well after reading a few of the threads here, I discovered that it is extremely hard to fool you guys. So this one will probably be a little too easy for you all.

A young man wants to join the army, and decides that the library is the best place to learn more about it. While strolling the aisles, he comes across a book with

VOLIX

written on it's spine.

What does VOLIX mean?

I know it's simple, but it's giving my mind a break from trying to comprehend all the math.^^

Volume IX?

Sorry, but that was just lame......