Harry Potter and the Order of the Phoenix has been replaced at the top of the UK book charts by controversial bestseller, Dr Atkin's New Diet Revolution.
The book came out on 21 June
JK Rowling's fifth Harry Potter adventure spent seven consecutive weeks at number one in the chart, published by UK publishing trade magazine, Bookseller and compiled with data from Nielsen BookScan.
But it slipped to third this week, with Minette Walters' novel Fox Evil jumping from seventh to second place.
Other Potter books still holding a spot in the top 40 are The Goblet of Fire at number 31 and the adult version of The Order of the Phoenix at 39.
Atkins shot to fame in the early 1970s
Dr Robert Atkin's popular diet book has received a lot of press coverage over the past week.
Some nutritionists have labelled the low carbohydrate plan dangerous, while other researchers say it is safe and effective.
The New Diet Revolution is the only book apart from The Order of the Phoenix to have sold more than half a million copies this year.
The fifth Harry Potter book broke UK sales records, selling more than 1,777,000 copies on its first day of release in June.
Other charted books include Yann Martel's Booker Prize winner, The Life of Pi, at number seven, and footballer Roy Keane's autobiography, which leapt from 66th to 11th place.