My advice....the 1.5 months after graduation is the last large block of free time you will have for a long time. Go somewhere you always wanted to go, spend time with family and friends, or camp out in front of the TV all day drinking beer. You will have enough time to read during your residency.
As far as anatomy goes, unless your program is OR-heavy for PGY-1's, you might be better off reading material that will prepare you for managing patients on the floors (ie fluids and electrolytes, micro, basic pharm). If the occasional OR case comes your way, then study the pertinent anatomy.
Good luck!