My copy of Quantum Mechanics and Path Integrals by Feynman and Hibbs just arrived! If, say, David Griffiths’ textbook epitomizes the ordinary “vernacular” treatment of quantum mechanics, QMaPI is a classic unorthodox approach. Intended for students who already have a bit of background in the subject, it builds up the Lagrangian alternative to the Hamiltonian method, a highly useful idea when one goes on to study field theory, string theory or advanced statistical physics.
For years, this book was only available in beat-up old library copies and illegal DJVU files from Lithuania, but now, Dover has brought forth a new edition. I’m not certain on this, but it appears as if the book was so heavily pre-ordered that Amazon.com sold out of it the day it became available for purchase.
EDIT TO ADD: One erratum — on p. 364, Thorber should be Thornber.