I had PM&R secrets, it's huge and has a good general overview of a lot of the stuff you'll encounter. I also used PM&R now through the AAPMR website. Google search should pull it up.. Lots of good high yield topics as well. Study up on your anatomy, nerve roots, action origin/insertion of muscles, dermatomes. Start getting familiar with the ASIA exam and perfect your neuro, mental status and MSK exams