tldr: This is notable because it's a high quality textbook being made available free to students, universities, and anyone else. Contrast this with what many

tldr: This is notable because it's a high quality textbook being made available free to students, universities, and anyone else. Contrast this with what many see as an inefficient commercial market for texts that are horribly expensive yet usually don't make the authors rich. The restrictions are minimal. Authors retain copyright, ask that no one profits from reselling, and that you don't post answers to the problems online. Betting pool open on how long the latter will last.