I hope this is the right forum to post this... I'm going through Wald's book in my first graduate level GR course, and am looking for lower level supplementary reading. I have a relatively strong math background, so Wald's language suits me well, but sometimes I feel like I need more elementary background in the physics (this is my first relativity course - I've never even taken special relativity before). I'm contemplating Schutz or Hartle. Which do you recommend as a supplement to Wald?