Spivak is great book and you can learn some deep ideas about calculus from it. It also has a separate detailed solution manual which can be very helpful with self learning. Another nice thing about Spivak is that it is a good prelude to some of his more advanced books like Calculus on Manifolds. On the down side Spivak's book is not a comprehensive as a good book on real analysis such as Elementary Analysis by Ross or Principles of Mathematical Analysis by Rudin. These texts lay out the deep theorems and definitions on which calculus is based in much more detail that Spivak. Courant is a great book that I would consider somewhere between Spivak and an analysis book but the exposition is not as modern and can therefore be a little difficult for some. All in all I feel the a basic calculus book like Larson followed by Spivak and the finished off by Ross is a great way to get a very deep understanding of calculus.