I finished it! This was hard work, partly due to Margolis's terse and somewhat technical style. He's not aiming to be a popularising communicator of pragmatist ideas here, which is just as well.
The book also (and this is probably due to its origin as a series of separately-published papers) meanders all over the place. At one point in stumbles across something like a central argument, then it tails off into a further series of digressions about tangentially-related arguments by Putnam, which Putnam himself has since disowned. Margolis is clearly a smart man and I found his arguments interesting at times, but I would have preferred a book which did a better job of keeping the bigger picture in view.