Apologies if this has already been answered.
I'm writing my GMAT in May 2012, so before the Integrated Reasoning section is implemented. For the Official Guide, should I buy the 12th edition or the 13th edition? If I buy the 13th edition, should I just ignore the IR section completely?
the IR session (50 practice questions) is merely an online addendum to the regular content of the OGs. Even with a 80-85% overlap, you still better go with the 13th edition. You are gonna have the same number of questions but you will be able to practice with this 15-20% of recently retired questions.