Where can you find a ninjutsu book?

I have been looking for one for some time now do they spawn in dojo’s or will I just have to hack a ninjutsu book in to learn it?

Military outpost barracks, though they’re not precisely common there.

If you’re playing in stable just hack the book. It won’t spawn anywhere in 0.B afaik

That’s correct, spawns weren’t in in time for stable.