Books that are given nicknames by grad students. :) For a foundational understanding of Calculus, and just becoming a better mathematician, a good start would be ->
Baby Rudin (Principles of Mathematical Analysis, Walter Rudin)
Papa Rudin (Real and Complex Analysis, Walter Rudin)
This reminds me of the Little Liddell and the Big Liddell of classical Greek scholarship fame.
The little Liddell is the small version of the famous Greek lexicon, while the Big Liddell is the big version. To make matters weirder, the small version is huge.
Baby Rudin (Principles of Mathematical Analysis, Walter Rudin)
Papa Rudin (Real and Complex Analysis, Walter Rudin)
Grandpa Rudin (Functional Analysis, Walter Rudin)