Somewhere in the labyrinth of obscure history and new-age philosophy that underpins Dan Brown’s latest book, the reader will find an emerging field of inquiry called noetic science. Employing “cutting-edge technologies”, this branch of neuroscience maintains that if a sufficient number of human brains focus in unison on a single task, then the boundary between mind and matter can be breached. Mountains, figurative and actual, can be moved. “Human thought can literally transform the physical world.”

Brown might be on to something here. After all, tens of millions of people believe his new book, The Lost Symbol, is a novel. This comes despite considerable evidence to the contrary, not least of which is the oddly defensive proclamation at the book’s beginning that “all organisations in this novel exist” and “all rituals, science, artwork and monuments in this novel are real”. Has any other mega-selling novelist ever felt the need to make it clear from the onset that he will not be employing one of the central conventions of his genre — the freedom to make stuff up?

This unease with fiction continues throughout the book, which involves Robert Langdon, the Harvard professor hero of The Da Vinci Code, travelling to Washington DC to do battle with a tattooed villain known only as Mal’akh, who has used his vast wealth and cunning to penetrate to the 33rd level of America’s Masons, allowing him to kidnap the group’s leader, Peter Solomon, who is also head of the Smithsonian Insti-tution. Mal’akh threatens to kill Solomon unless Langdon, the victim’s close friend, helps him uncover the encoded secret being kept hidden deep in Washington by the powerful Masons. The CIA soon enters the fray, suggesting that the Masons’ family jewels are not simply club secrets, but have far-reaching national security implications.

Although the story sometimes has the pace and structure of a thriller, it is at heart a guidebook to the hidden bits of America’s capital, with Brown serving as both lead-footed bus driver and garrulous tour guide. See that neogothic building over there, from which Langdon and Solomon’s leggy noetic scientist sister, Katherine, emerge, pursued by a CIA helicopter? That is the Washington national cathedral, “the sixth largest cathedral in the world”, which contains “a 53-bell carillon, and a 10,647-pipe organ”. If you look to your left, at the building currently being penetrated by an emblazoned eunuch carrying a severed human hand, you will see the Capitol, for whose secret catacombs two maps are provided. After that, we will arrive at the House of the Temple, the majestic Masonic headquarters, where you would be advised to be on the lookout for falling shards of glass resulting from a blast from an electromagnetic pulse-gun wielded by a surgery-scarred Japanese-American CIA agent.

While Brown was largely able to get away with this authorial sleight of hand in The Da Vinci Code, it now feels as if the pedant has overtaken the storyteller. Langdon is also a curiously wan and passive presence, good for lengthy disquisitions and not much else. His escapes from various pickles are usually thanks to Katherine. He even admits as much to her near the novel’s end: “You know I didn’t do anything, right?”

The plot itself turns out to be oddly inconsequential. What saves the book from foundering completely is the well-handled story of the Solomon family, which provides several surprising twists and some rare moments of real heart. But it is after Brown’s tale reaches its conspicuously tepid climax that he plays his true hand. The book abandons all pretence of thrilling the reader and degenerates into 40 pages of gooey noetical nonsense that is delivered as Langdon pays dawn visits to various Washington high points. The vistas are spectacular, to be sure, but not even a billion minds working in unison could turn it into a novel.

The Lost Symbol by Dan Brown
Bantam £18.99 pp509

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