This is the edition you want.
If you're looking for a downloadable PDF version, I must remind you that sharing or downloading copyrighted materials without permission might be against the law. However, you can try: classical mechanics by goldstein pdf
This is the edition many older professors learned from. It is rigorous but dense. The typesetting is old-style, and some notation is archaic. However, many pure theorists prefer the 2nd edition's no-frills approach. This is the edition you want
The end-of-chapter problems are legendary for their difficulty. Many physics departments use problems directly from the 3rd edition for their qualifying exams. Working through a "Goldstein" problem requires physical intuition, rigorous math, and patience. and some notation is archaic. However
If you are looking for a digital copy, you’ll likely find three different editions: