I don't know about Family Medicine, because I don't take that until February. In general, the shelf exams have very little basic science -- they're almost nothing like Step 1. The most science that they have is usually relating to physiology or pharm, but even that is in more of a clinical context. My general advice is to pick up a good step 2 review book, read throughout the clerkship, and pay attention on the wards, particularly regarding patient management.
The surgery shelf exam puts a lot of emphasis on trauma, burns, and fluid and electrolyte management. Besides the expected general surgery questions, they also expect you to have some basic knowledge of the subspecialties -- in particular neurosurgery, ortho, and peds surgery. Let me emphasise the word basic in the previous sentence -- don't go crazy learning the subspecialties inside and out -- they just want you to know a few of the most common things seen in those areas.
For my surgery rotation, I also used Surgical Recall (essential for that rotation). But the main reading source that I used was called "Essentials of General Surgery", and I can't remember the author right now -- I'll take a look when I get home and repost. The book has a black background, and has a picture of one of those old famous paintings of surgeons operating in front of a sort of lecture hall. It has a great review of trauma management, fluids/electrolytes, burns, and many of the general surgery topics. The main areas that it's lacking that you do need to know are neurosurgery, ortho, peds surgery (but surgical recall contains those topics anyway). But overall the book is really helpful.