questions are similar to GMAT CR questions but are generally more difficult. They do share the same types of questions (e.g. both have weaken, strengthen, must be true, assumption, justify the conclusion...) question types, but the LSAT includes some additional CR question types not found on the GMAT (formal logic, parallel reasoning, etc.)
For most people, using the MGMAT CR
guide or Powerscore CR
guide will be sufficient in prep. If you really want to ace the CR section though, Powerscore has a LSAT Logical Reasoning
Bible that is 400+ pages devoted exclusively to CR (in Lsat it is called logical reasoning).
So, yes, they are similar but unless you're aiming for 750+ it probably isn't worth it to review the LSAT bible. If you do find yourself struggling in one particular question type, however, it would be useful to flip to that portion in the LSAT guide since they cover question types extremely well.