Which book are we talking about?
In general, LSAT LR is quite similar to GMAT CR, if you stick to the common GMAT questions--Assumption, Strengthen/Weaken, and Inference/Conclusion. Some of the related topics are good, too--Flaw, Evaluate the Argument, Analyze Argument Structure, & Explain a Situation. However, these less common types show up more on the LSAT. The LSAT also deals more with very abstract reasoning and conditional logic (If-Then statements). It also has more problems asking you to match the reasoning (pick another argument with the same structure) or explain what two parties agree or disagree about. This is all good for your reasoning skills, but it may not pay off directly in a great GMAT score. Use the rare stuff sparingly and don't worry about the farthest-out material, and you'll have a nice source of tough CR problems.
I hope this helps.