If you find an error, please let me know. There seems to be an unending supply of them. As one author described it brilliantly, “the hand is still writing though the brain has long since disengaged.”
Also let me know if you find points that are unclear to the intended readership, mechanical engineering graduate students with a typical exposure to mathematics and physics, or equivalent. Every section, except a few explicitly marked as requiring advanced linear algebra, should be understandable by anyone with a good knowledge of calculus and undergraduate physics.
The same for sections that cannot be understood without delving back into earlier material. All within reason of course. If you pick a random starting word somewhere in the book and start reading from there, you most likely will be completely lost. But sections are intended to be fairly self-contained, and you should be able read one without backing up through all of the text.
General editorial comments are also welcome. I'll skip the philosophical discussions. I am an engineer.
Feedback can be e-mailed to me at firstname.lastname@example.org.
This is a living document. I am still adding things here and there, and fixing various mistakes and doubtful phrasing. Even before every comma is perfect, I think the document can be of value to people looking for an easy-to-read introduction to quantum mechanics at a calculus level. So I am treating it as software, with version numbers indicating the level of confidence I have in it all.