I don't think just "a book" is a good advice for deprograming the anticommunists, the bookstores and libraries are full of anticommunists lies pretending to be true by virtue of nearly entire academia of anticommunists and state/publishing market censorship of communism.

Like in Poland we had something like 5 communist publications in 36 years, of which three were printed in very small numbers, one was accidental selfown by illiterate succdems and one was highly contextual. For comparison Orwell shit or Ossendowski slander against Lenin has literally new edition every year.

You would need to be more specific, unless you want them to read Pipes, Montefiore or one of the million other propagandists of capitalism.