A retraction.

He also posted an eight-paragraph note on the book’s Amazon.com sales page, calling it “a misguided and potentially dangerous publication” and expressing his wish that the book be taken out of print.

And from wikipedia:

[…] he began writing about pedagogy and conflict resolution. This led him to renounce his book and instead campaign for its withdrawal from publication. He was unable to legally stop the publication of The Anarchist Cookbook because the copyright had been issued to the original publisher Lyle Stuart, and subsequent publishers that purchased the rights have kept the title in print. Powell publicly renounced his book in a 2013 piece calling for the book to “quickly and quietly go out of print”.