The book was out of print for a while, and this PDF was the only way to,read it for less than $400. But now it's back in print for $17: https://www.amazon.com/dp/0813595835/ Basically the same content, highly worth reading in either format.

He addresses the calamity that engineers don't read several times in the book - formulations are attempted a few years after someone proved it didn't work. Makes me wonder if a similar approach wouldn't be advisable in programming...