This is a fascinating, illuminating, even exciting work. I'm giving it 5 stars, but with the caveat that occaisonally Schwinger's thought process merely left me confused. I'm sure that had he lived to finish the book those few snags would have been worked out with the editors.

One interesting feature is that, once he starts getting into applications,
derivations are worked out in great detail, which may make the book look more mathematically dense than it really is. It's all pretty accessible to anyone who has had undergrad QM. There are also tons of exercises (no solutions, though.) This would make a great supplement to a book like Sakurai's that takes a more deductive approach. I could even see a talented instructor using it as a primary text.