"How To Build a Great Bowstring" is the second one. We thought about calling it "Doin' the Twist II", but decided to go with a name that was more to the point.
They both contain some of the same information, but they both also have information that you won't get from the other.
DTT includes instructions on a homemade endless jig, tying a bowyer's knot, plans for a stretching jig, and two slightly different techniques for twisting up flemish strings.
BGB has better camera work, especially better close-ups, and goes into more detail about endless strings.
Both cover 2 and 3 bundle flemish strings, endless strings, serving, plans for making a flemish string board, installing silencers, etc.
The first one we did (going on 7 years ago) was Joe Stark, formerly of Lone Wolf Traditional Archery (retired now) and myself. The new one features Rod Jenkins and me, and was filmed and produced by Traditional Vision Quest (Denny Sturgis Jr. and Darryl Quidort).
I think you can learn to make a string from either one, but if I had to choose I'd go with "How to Build a Great Bowstring" due to the camera work being much better, and I think it's easier to watch. It also has a "blooper" segment that will make you grin.
Chad