Here is a list of books which I like (other than Milnor, of course):
* _Morse Theory and Floer Homology_ , Audin, Michèle, Damian, Mihai
* _An Introduction to Morse Theory (Translations of Mathematical Monographs, Vol. 208)_ , Yukio Matsumoto
* _An Invitation to Morse Theory_ , Nicolaescu, Liviu