Hi arwma,
The official guide is a nice book for practice; however, to truly master the GMAT, you will likely need some additional, more robust prep materials.
With that in mind, when it comes to test prep resources, it’s important to find the one that best suits your learning style.
This article explains the different prep resources you can use:
GMAT Focus Study Resources: Your Guide This article explains what to look for when choosing a prep course:
Best GMAT Focus Edition Prep Courses Online: What to Look ForFinally, in addition to chatting with folks here, you can check out GMAT course reviews on GMAT Club. Most courses also offer free or low-cost trials so that you can give a few a test drive.
If you have any other questions, feel free to reach out.