An Introduction to Morse Theory (Translations of Mathematical Monographs, Vol. 208)
"The first two-thirds of the book is accessible to anyone with knowledge of calculus in $\mathbf{R}^n$ and elementary topology. The book begins with the basic ideas of Morse theory ... on surfaces. This avoids some of the technical problems of the higher-dimensional case ... and allows a very pictorial introduction. The text, which was translated in part by Kiki Hudson, and in part by Masahico Saito, is very readable." ---- Mathematical Reviews