Don't judge a book by its cover

This proverb means that it isn't always proper to choose a person or something merely by appearance.

Just due to the fact the cover of the book is stunning or attractive, This does not mean that the content within it will be of enormous and high value and vice versa.

A simple book may contain invaluable information. To realize this, one must read the entire book.

Likewise, one must deal or interact with a person before deciding on his abilities, personality, and talent.