In what direction is Japanese usually written in books?
I thought it was written like in English, horizontally left to right, but I saw a (story) book in my Japanese class (last summer) that was written vertically right to left. How common is this? Does it depend on the kind of book? What about novels? The vertical way must take a lot of space...
I think the main reason that Japanese (and Chinese) started being written horizontally was that it is very inconvenient to include Roman text or scientific/mathematical notation in the vertical format. In situations where it isn't necessary to do this, however, writing vertically is just as space-efficient, as all characters tend to occupy identical squares that will happily stack in either orientation.
When written vertically, the writing system is top to bottom, and right to left. When written horizontally, the writing system is most often left to right, similar to standard English text. In the early to mid-1900s, there were infrequent cases of horizontal text being written right to left, but that style is very rarely seen in modern Japanese writing.