Buy a used Schaum’s Vector Analysis (any edition from 1980 onward) or borrow it from a library. Work through the solved problems, then try the supplementary problems – you can check your answers in the back. That is the intended, legal, and effective way to use Spiegel’s work.
Would you like a list of free, legal vector analysis resources (e.g., MIT OCW, Paul’s Online Math Notes) instead? vector analysis by spiegel solution pdf