[tzs]

> As the author mentions, you can pick up a copy for well under $20.

It's a Dover edition. They love getting textbooks that are decades old and making inexpensive but decent quality paperback editions. In fast moving fields Dover editions may be out of date, but if the fundamentals haven't changed much a Dover book can be a great way to get started.

To a good first approximation if you are interested in some area of STEM and would be fine with an approach that doesn't include the last couple of decades are so of developments Dover is a good place to start.