The book Starting Strength is about the specifics of a novice barbell program. It is very complete on how to learn the lifts, how to program them and to progress until novice linear progression is exhausted, and very little beyond that.
The book Practical programming for strength training is not about how to do the lifts. It is about how to program barbell training, depending on how advanced is the trainee (from novice to some examples of advanced programming).
I have and like both. The only downside of PPST, to me, is that it is heavily biased toward barbell, and to the model stress-recovery. It leaves little room for high frequency "neuronal efficiency" programs, like PTTP, S&S, and many strength programs without barbells (although the principles could still apply).
Still a good and recommended read for anyone who is serious about strength programming.
For more questions, I would go to Rip's website.