I'm looking to get a copy of a classic physics text that will serve as good preparation for the elementary subjects on the pgre(mechanics, thermal, optics). I see Griffith's gets recommended a lot for E&M and I've got most of the modern subjects covered, but what edition of Halliday's Physics should I get? The cheapest edition I've found is the 60's-70's "2 volumes in one" edition which I'm thumbing through right now. Are the more modern editions with Walker or Krane significantly better for pGRE preparation? I believe Krane's has more questions especially of the multiple choice type, would that be a better choice?