"[9] The most "telling criticism," in Hinsliff's view, was that "Corbyn is simply not very bright... His backbench career was long on expressing passionate solidarity with causes but short on concrete achievements, and he comes across as prone to ducking arguments that he lacks the skill to win."

She argued that the book's greatest flaw is Bower's eagerness to condemn its subject, but concludes that Dangerous Hero, "is the most compelling in-depth study so far of a man whose head is unusually difficult to get inside, given his suspicion of anyone who isn’t a fellow traveller.

"[9] Ex-Labour MP Tom Harris wrote that the book is a "meticulous and highly readable account", that "stands as an indictment of both the Labour Party and a political system that allows an individual such as Jeremy Corbyn to come within shouting distance of the levers of power in the UK".

[10] In June 2020, it was announced that Associated Newspapers, the publishers of The Mail on Sunday and MailOnline, paid substantial damages and costs over a "grotesque" libel made against a non-profit Palestinian refugee group in its serialisation of the book.

Lawyers for the plaintiff, the Palestinian Return Centre, said: "Neither Mr Bower, the Mail nor HarperCollins (the publisher of the book) saw fit to properly verify the true position, nor to put the allegation to the PRC prior to publication."