Looking for a book on Calculus

Well, the OP asked for more theoretical calculus books, which is why I originally shied away from giving reccomendations on “advanced calculus” or real analysis texts (advanced calculus being distinguished by reworking pretty much all of a standard three-course sequence in calculus from the axiomatic description of the real numbers on up).

If he’s looking for a good introduction to proofs and so on, I’d actually recommend looking into an abstract algebra text rather than advanced calculus, despite the analysis-addicted current vogue.