Attached is a picture from the on-line guided lessons for Maurer's "The Sanskrit Language".   It shows a  book with  text  oriented in the book 90 degrees different from the normal orientation in most western books.  I've seen this orienttion in some small devanagari chanting books.  I'm curious how common this orientation is, if it is only used for chanting books or if it is a feature of certain publishers or any other information.

Thanks,

Harry Spier