I use Anki to study all kinds of subjects, and more than half of the value is processing what I learned (usually with pencil and paper) into good anki cards ("atomic", as per Michael Nielsen's definition), including the insights that I had when studying the subject (like "what's the comparison with X that I used to understand Y?")
I'm not sure if it is efficient, mind you, but I suppose it's effective because I can recall information later when relevant, and I believe that like exercising just being able to stick to a study routine ends up being more important than picking the best routine