TTP is an excellent resource for structured GMAT prep, especially if you have four months to prepare. It provides a comprehensive approach to both Quant and Verbal, ensuring strong concept reinforcement. However, its mandatory to complement your prep with official GMAT questions.
That said, almost all problems from the Official Guides are already available on GMAT Club. You can filter by the "Official Guide" tag and practice them there instead of purchasing the books separately. This way, you get access to high-quality, real GMAT questions while using TTP’s structured approach for concept mastery.
Best of luck with your prep!