Take the tour ×  I just graduated from an engineering school and
am about to begin classes as a PhD candidate. As I review my
undergraduate classes and sift through old notes, I find myself
wanting for more math knowledge. While I did well in math
classes, I always felt as though I was following steps rather
than gaining a depth of understanding and intuition. To get to
the point:  Can you recommend any books to brush up on and
perhaps gain a more advanced understanding of calculus and PDEs?
As an undergraduate, I used Salas Hille and Etgen, which I felt
was great at teaching rote steps to solve problems but lacked
some depth.  Thanks in advance!  (Questions regarding a
reasonable self-guided book have very frequently been brought up
on this forum. However, I like to think this is unique and
apologize if this feels "repeated.")  share|improve this
question add comment  1 Answer  up vote 2 down vote accepted  If
you are looking for a depth of understanding of PDEs, I would
suggest Partial Differential Equatio