I waited until I read the first three volumes of the manga before listening to this. It was an arbitrary decision, but it turned out to be a great move! This does not directly follow the manga story, but uses elements from the manga throughout, so familiarity with the characters and the basic story is required. First three volumes of the manga turned out to be just right amount of preparation.
To get to the point, this is very nicely done! My expectation of the anime went up a few notches after listening to this and I believe it's going to beat it.