Opposite

I know I won't be the first to spot the possible irony in this but I hadn't seen this book until about eight hours ago:

This is what you see on the front cover of a book by Paul Arden:

Whatever you think think the opposite: Paul Arden author of the world's best selling book.

Does that mean it's the worst selling book then? Or that we are meant to believe it is the worst selling book?
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