I'd recommend doing a search for posts that discuss the Logic Games Bible. There've quite a few posts that "review" the book. I can honestly say that I don't recall reading any bad experiences/impression of the book. Granted, my opinion may be biased but for good reason.
I've used it, and it was worth every penny I paid for it. I don't know about whether it conflicts with Testmasters or not, but I figure there is no single "right" way to study for the LSAT. At the very least, it can't hurt!