This is based on second half of one of the greatest manga ever written. They left a lot of the story out because they only had 24 episodes total, and while that included some of my favorite parts the heart of the story is all present.
Let's just get this part out of the way. The animation sucks. All the CGI from the first season is gone and everything has been replaced with stills for the most part. They show motion by overlaying some moving bubble layer on top of the audience and pianist whenever music is being played, and by panning over still pictures.
There's very little actual animation.
The best part of this is the performances. They got some of the best young pianists from around the world to stand in for each of the different performers and they did incredible jobs. If you like classical piano this is worth watching for that alone. Or maybe buy the CDs.
I'm happy that they finally animated the entire story, if you can call this animation. But really I think what would be the best way to experience this would be to read the manga while the music from the anime is playing in the background.