Traditional writing is vertical, top to bottom, right to left. Most writing created with computers is horizontal, left to right. In the bookstore, you’ll see two kinds of books, those where you turn the page from left to right, usually reserved for fiction or essays, and western style, which are like the books you are familiar with, where you turn the page from right to left.
In pre-war Japanese, it was common for horizontal writing to be right to left as well. This always gives me a headache whenever I try to read it.