Of course, the "Complete" 2-CD set is the one most people buy. But, as other reviewers have noted, the sequencing of release takes and alternates on that product is disconcerting. This budget CD has the best version of each of Robert Johnson's 29 songs. Songs are grouped by session but within each session are arranged for the best listening experience. And the sound is, considering the age of the recordings, as good as one could hope to expect--which is very good indeed. Usually not available directly from Amazon but can be quickly obtained from the listed sellers. I bought mine from CD Zone (UK) and it arrived within 10 days.
If you want to have something to sit on your shelf as an indicator of your good taste, get the box set. But if you want to really get into the music of Robert Johnson and understand his legacy, buy this CD.