The GMAT Official Guides do not differ from each other significantly year-on-year. There are minute changes in the subsequent editions every year.

There are about 10% more practice questions that are added in every component of the GMAT Exam (Problem Solving, Data Sufficiency, Sentence Correction, Critical Reasoning, Reading Comprehension), to keep up with the latest GMAT paper pattern.

However, the conceptual/theoretical part of all the sections in the GMAT Official Guide largely remains the same.