You can't judge a book by its cover.

不能凭封面判断一本书（的好坏）。

You can't judge a book by its cover.

不能根据封面判断一本书。

You can't judge a book by its cover.

不能根据封面评判一本书。

You can't judge a book by its cover .

不能根据封面判断一本书。

You can't judge a book by its cover, ever.

你们永远不能以貌取人。