i just pretty much finished this prelude and fugue. I have the Dover edition of WTC 1 and 2, and it's easier to read, I think than others that I've seen. You need to think of the barred sixteenth note figures as a response to the eighth notes. I don't know if I'm explaining this well. Basically, measure 11 rythmic imitation of the descending bass just a measure or two earlier.
This is my favorite prelude.