Pork shoulder is one of my favorite things to make. I hope this opinion doesn't come too late for you.
The sauce in the book is more or less a plain-jane North Carolina-style pulled pork sauce. In that style, vinegar-based sauces dominate, mainly because it works so well with the texture of the meat. See, you're pulling the meat into the individual muscle fibers, and because the meat's been cooking so long the fibers are going to be dried out (the eater doesn't notice, because hopefully the fibers are coated with lip-smacking gelatin from all that dissolved collagen in the meat). However, when you shred the meat odds are the gelatin will start getting lost, so you put a liquid-type sauce there to help compensate. Because the meat is shredded it will absorb that sauce much easier, much like a sponge. Now if you use a more viscous sauce, like a KC Masterpiece-type sauce, the meat won't really absorb it well, and you're left with strands of dry meat floating in thick barbecue sauce. Further, the thicker barbecue sauce will tend to dominate and the smoky, pork flavor you've worked upwards of 4 hours to create will get lost.
Now, I've made the sauce in the book a few times, and end up putting more sugar in it to make it more appealing to my victims...I mean, guests. Unless you're writing off vinegar sauce totally (in which case I'd suggest using a brine for your pork shoulder next time and skip the sauce entirely), try adding some brown sugar to it to kind of cut the vinegar taste.