Apparently it is a well known feature of Glenn Goulds work that he hums along to his playing. If you can ignore this then you'll be fine and can enjoy some well played pieces.
I bought this for my wife, who wanted to get back into playing the piano and chose the two and three part inventions as a starting point, she was less than happy to hear the humming, found it distracting and hasn't listened to them more than a couple times.
Having really enjoyed Gould's performances of the Goldberg variations I was looking forward to this recording. It's probably not fair to compare the two as they are very different pieces of music, but I just could not get as enthused about this recording as some of his others. I can't fault Gould's playing but there seemed to be something missing for me.