Do you think that listening to a lot of different things in a language is an efficient way to improve it?

I wonder whether listening to audiobooks is really useful compare to reading the book. It seems to me that listening to such material is rather a clever way to relax than an efficient way to learn the language. I don't mean it is not useful at all but I doubt that is as efficient as it is said. What is your opinion? What is your experience about this matter?