As previous reviewers have said, Weinberg's book is excellent for somebody with previous exposure to QM, and as rigorous as possible (for a book at this level).<br><br>I would just like to add that there are a surprising number of applications in this book: the Lande g-factor, rigid rotor, even Landau levels, Bloch theorem, and Fermi/Bose occupation levels, which all three of which I did not expect to find. Even an introduction to quantum computation! As such, this book is excellent as a reference, and not just for purists.<br><br>Finally, Weinberg notes that he purposely left out the Dirac equation and relativistic QM (standard graduate material) because they are better learned in the unified context of QFT. Though this is true, perhaps somebody just wants people to buy his QFT books ;)