Dan Brown's follow-up to The Da Vinci Code has sold more copies in its first 36 hours of UK release than any other adult hardback novel, say publishers.
The Lost Symbol, which went on sale on Tuesday, has shifted more than 300,000 copies in the UK, Transworld said.
Publishers said sales in the US, Canada and the UK had already topped 1m, amid claims of record-breaking sales of the digital edition in the US.
The Lost Symbol is Brown's first book since 2003's The Da Vinci Code.
Set in Washington DC, it once again features Harvard symbologist Robert Langdon, this time delving into the secret world of the Freemasons.
"We are seeing historic, record-breaking sales across all types of our accounts in North America for The Lost Symbol," said Sonny Mehta, editor in chief of US publisher Knopf Doubleday.
In the US, both online retailer Amazon and booksellers Barnes & Noble claimed record one-day sales for adult fiction.
However, the book fell well short of sales figures of JK Rowling's Harry Potter and the Deathly Hallows, which sold more than 8 million copies on its first day in the US alone.
"The biggest surprise was that, despite sustained, strong physical book sales, on Tuesday we saw the Kindle [electronic reader] edition outsell hardcover editions on the book's release day," said Amazon spokesman Andrew Hardener, referring to strong e-book sales in the US.
His calculations, however, did not include pre-orders.
Sony spokesman Kyle Austin also claimed The Lost Symbol set a single day record for e-sales, outselling other releases more than 10 times on Tuesday.
Doubleday released the digital edition of the thriller, despite industry concerns that the lower priced e-book could harm sales of the hardback.
The Da Vinci Code has sold 81 million copies around the world and is the UK's biggest-selling paperback of all time.