I've decided to major in Physics and just finished E&M as well as Calculus 3. I understand how to do most of the problems in my Calc book (the same text was used for all three courses) mechanically. Our classes used James Stewart's text and I had Ron Larson's as another reference. My concern is that I've read on these forums that there are other Calculus books that go more in-depth into the subject. Personally, I feel that not studying from these books can lead to me being at a disadvantage when I start taking 3rd year and beyond Physics courses. Is this the case where certain "proof heavy" books such as Apostol's, Spivak's and Courant's would benefit a Physics major more than Stewart's and Larson's? I'm aware that there are those that were fine with just reading Stewart's and/or Larson's, but how about the ones who have studied from the other Calc books mentioned? Any insight would be much appreciated.