Manga is normally right to left (both pages and lines) because it's written with vertical text. "learn statistics through manga" type books are left to right because they're written with horizontal text (because of formulas, etc.).

(I don't know if I agree with the comment you're responding to, by the way.)

It's irrelevant for computers because text on computers is basically always left to right though.

EDIT: huh, I opened a couple manga I had nearby and my original post was dead wrong

> Text within speech bubbles is generally left to right.

This isn't true in Japanese which is what limteary was asking about.

Horizontal text in modern Japanese is virtually always written left to right.

The primary exception is where the context of the writing itself implies a direction, e.g. text on the passenger side of a bus, or on a directional sign pointing to the left, may be written right-to-left so that the text "flows" in the same direction as its container. This would never be used for a longer text, though.