You could also try the PowerScore CR Bible - I personally found that it was the only book that really nailed the GMAT style in questions. It also provided some very neat tips and strategies not only for CR, but also RC. As a matter of fact, PowerScore is highly respected for their LSAT material - and the LSAT does brush with the verbal part of the GMAT to some extent (but LSAT questions tend to be more difficult). I haven't had the chance to check out their other guides though - the SC one and the general verbal one...
Many people on this forum also recommend MGMAT, particularly their SC guide. If that's your weakness, maybe you want to buy that book as well. I understand it also comes with access to their 5 or 6 tests (I'm not sure exactly how many), so most people would say it's good value for your money.
