Feynman's "Quantum Mechanics and Path Integrals" is about $18 on Amazon
http://www.amazon.com/Quantum-Mechanics-Path-Integrals-Emend...
That is a serious graduate level book - written in his own style.
http://www.amazon.com/Quantum-Mechanics-Path-Integrals-Emend...
That is a serious graduate level book - written in his own style.
"...recasts many equations for clearer comprehension" to me is an unacceptable modification.
Caltech has this available: http://authors.library.caltech.edu/47756/1/FEYrmp48.pdf
There are some other good treatments too, although I can't find them at the moment.