Is a thesaurus book that tells you the opposite of word are researching?

A thesaurus doesn't typically provide the *opposite* of a word, but rather synonyms (words with similar meanings).

To find the opposite of a word, you're looking for its antonym. While some thesauruses might occasionally list antonyms, they are not their primary focus.

There are other resources, like dictionaries and online antonym finders, that specifically provide antonyms.