When the curtain comes up on Mark Rosenblatt’s superb debut play, Giant (commandingly directed by Nicholas Hytner at London’s Royal Court Theatre), Roald Dahl, the six-foot-six giant in question, is hunched approvingly over the galleys of his latest children’s book, The Witches, working on changes to Quentin Blake’s drawings. “Much nastier. Blistering scalps, clawed fingers, good. And her in the middle. Relishing the bloodlust to come,” he says to his oleaginous British publisher in the play’s first beats. That turns out to be Rosenblatt’s game plan, too. He is telling a tale of bloodlust and monstrousness of a different kind.

The word “monster” has its roots in the Latin for “blessing” and “warning.” The blessing of Dahl’s storytelling genius is transparent in his 48 books, which have sold around 300 million copies worldwide, and the rights to which were bought by Netflix for a reported $1 billion. The warning is in Dahl’s unabashed anti-Semitism, which emerged in a 1983 interview with The New Statesman, as he defended his anti-Israeli statements in a previously published book review. This scandalous event, which hit the newsstands just as The Witches was about to go to press, is the play’s inciting incident.