That would be board review books for PBL 8)
I'm serious. Start studying for boards on day 1. I did and I passed step I and Step II on my first go around.
Get you a Cecil's Essentials of Medicine, Pharmacology Recall, Micro Recall, some pharm and micro flash cards and USMLE Secrets Step I and Step-Up to Step I.
Learn your pharm and micro and then use your USMLE Secrets Step I and Step-Up books to "Guide" your group and your daily "learning issues" to relevant topics.
If you have a gunner in your group who wants to study the molecular structure of the individual tumor markers involved in Colon Cancer, promptly take the heaviest book in sight and beat her senseless over the head during wrap-up. 😉