Although celebrated by some reviewers, I think Backhaus' box set doesn't excite the listener. Several movements are played too fast as if he had no patience or time to play (or record) them at the correct tempo marking.As far as recording is concern, there are differences among the sessions like mics placement and reverb. On the majority of the tracks, unfortunately, the piano sounds like an old and harsh fifth rate instrument.If you still doesn't know the Beethoven sonatas, I suggest starting from the Arrau's box set; if you're an expert and are looking for another version, check the amazing Anton Kuerti's recordings.