Ms. Walker’s response did little to dispel the controversy that erupted after she gave an enthusiastic endorsement of Mr. Icke, a British conspiracy theorist.

“There is no fair reading of Icke’s work that could be seen as not anti-Semitic,” Jonathan A. Greenblatt, the chief executive of the Anti-Defamation League, said in an email on Friday. “Public figures should not be making excuses for Icke’s hatred; they should be condemning it.”

In the book, Mr. Icke draws on ideas from the anti-Semitic pamphlet “The Protocols of the Elders of Zion,” argues that Holocaust denial should be taught in schools and that Jews are responsible for organizing anti-Semitic attacks, and calls the Talmud a racist document. In other writings, he has posited that a cabal of a child-sacrificing, bloodthirsty lizard people, many of whom are Jewish, are secretly running the world.

Ms. Walker did not immediately respond to an interview request submitted through her literary agent on Friday. In response to an interview request to Mr. Icke, his son sent a link to a recording of a statement this week in which Mr. Icke denied being an anti-Semite and argued that the criticism amounted to “propaganda against me designed to discredit me and what I’m writing,” but went on to say that “some Jewish people are involved in a global conspiracy.”

In last week’s By the Book column in The Times’s Book Review section, when Ms. Walker was asked which books she has on her nightstand, Ms. Walker cited “And the Truth Shall Set You Free,” saying that “in Icke’s books there is the whole of existence, on this planet and several others, to think about.” In the same answer, she also praised “The Road of Lost Innocence,” a book about sex trafficking in Cambodia by Somaly Mam, which was discredited in 2014 when it emerged that Ms. Mam had fabricated parts of her story. (Ms. Mam denied the charges but resigned from her namesake foundation after an investigation.)