Alibris link:
https://www.alibris.com/search/books/isbn/9780534944469?invi...
That's for the 2nd edition, which is what I have. There are 3rd and 4th editions out now. There may be cheaper used copies available, I didn't spend a lot of time searching.
Review by The Math Sorcerer:
https://www.youtube.com/watch?v=FPr5-X9nZc4