Robert Langdon is a symbologist, and that is the meta joke – the only joke – of Dan Brown’s series of blockbusters, of which this is the sixth. Langdon, an Everyman – Frodo Baggins but taller, and with a professorship at Harvard – is a monied, moderate intellectual who likes swimming. And he is very ordinary – until he isn’t.

All novels have subtexts, even if they don’t really want them. They can’t help it. This one is: a monied, moderate intellectual can be interesting, and interesting things can happen to him. (I think Brown spends a lot of time at his desk. I also think he prefers ideas to people.) Langdon can set off the fire alarm in his hotel and jump out of the window into the river. He can be stalked by the Golem of Prague (it’s nice to have a Jewish hero who speaks. In. Very. Short. Sentences). He can have sex with a woman who calls him ‘Aquaman’ and can wonder why she shaves her legs. (Unlike his pulp fiction hero Sidney Sheldon, Brown doesn’t really do erotica, which is a shame.)

There’s an innocence to Langdon, which is easily mocked, but it’s essential to his success. We could all be Robert Langdon if we were only a bit better at pub quizzes. Even after Angels & Demons (antimatter in the Vatican), Langdon is still capable of being surprised, and when he is surprised he thinks in italics: Is the universe taunting me? Or: She’s shaving her legs?

This time Langdon is in Prague doing European things when his girlfriend Katherine, who is about to crack the secret of human consciousness – the secret of secrets – is abducted. The book is so thick with villains I can’t remember who abducted her, but it has something to do with a programme called Threshold, which is ‘the Manhattan Project for the future of brain science’. (‘You’re saying consciousness is like a streaming service to which our brains subscribe?’) Langdon must leave his comfort zone again, find Katherine and penetrate Threshold while being chased by the CIA, a hotel manager who is still furious about the fire alarm and the Golem. He does this by visiting the main tourist sites in Prague while in terrible peril, which makes me wonder if the child Dan Brown went on some nightmarish city breaks.

Brown does not write characterisation, he writes plot; and if you think he writes badly, consider what happens when he tries to write well. Langdon’s friend contributes a piece to the New Yorker about the collapse of literary standards: ‘To save a single keystroke by typing “gud” instead of “good” is not only indecorous, it is an abomination of indolence.’ This is the place to tell you that Brown is also the co-author (with his ex-wife) of 187 Men to Avoid: A Survival Guide for the Romantically Frustrated Woman under the pseudonym Danielle Brown. If you want to know what the secret of secrets is (the title is nicked from a fake Aristotelian treatise dedicated to Alexander the Great) it is this:

Your brain is just a receiver – an unimaginably complex, superbly advanced receiver – that chooses which specific signals it wants to receive from the existing cloud of global consciousness. Just like a wifi signal, global consciousness is always hovering there, fully intact, whether or not you access it.

‘You’re saying there’s a golf channel in the universal consciousness?’

‘I’m saying everything already exists out there….’

Now this does, too.