Calculus: Multivariable

McCallum's approach to multivariable calculus is one of my favorites. This book is short on rigor (maybe five proofs in the whole book, and these are in separate sections), but instead focuses on using approximations to develop formulas followed by limits to make these formulas exact. It really focuses on the "why" without getting bogged down in complete proofs or problems that are difficult for extraneous reasons. Also, the book avoids distracting margin notes and confines itself to perfectly adequate two color printing. This saves on costs and focuses the reader on the exposition.