If you're looking for a way of tracking your progress with the Official Guide, try this online tracker:
http://www.gmatpill.com/official-guide-gmat/
The gmatpill og13 tracker lets you go through all the questions with an online timer and then post comments for each question. Some questions have video explanations.
http://www.gmatpill.com/official-guide-gmat/
The gmatpill og13 tracker lets you go through all the questions with an online timer and then post comments for each question. Some questions have video explanations.