Kate McCann's book about her daughter Madeleine's disappearance has sold nearly 400,000 copies and raised up to £1 million for the fund to find the missing child.
Mrs McCann thanked supporters for buying her account of how her daughter went missing on holiday in Portugal, which was published in hardback a year ago.
She said: "The book has done amazingly well. That's thanks to the general public, and I'm really really grateful.
"Not only obviously has it helped Madeleine's Fund, more importantly it's got people engaged again.
"There's more awareness now, there's more information still coming in now.
"For a long time we had wanted to correct things that were incorrect, just so people could be better informed, and therefore the search enhanced."
Her husband Gerry added: "It's put everything in the right context. So much in this case has just been taken as snippets and taken out of context.
"It's a properly considered record of what we've gone through, and Kate's done a brilliant job."
Mr McCann, 43, said: "I think the most important thing is that a lot of the investigation opportunities are in Portugal.
"I think it's fairly clear that the case will have to be reopened for those to be pursued adequately.
"I have no doubt about that. It will get reopened."
Above: Scotland Yard released this computer-generated picture of what Madeleine may look like now
Mr McCann said sales of the book, simply entitled Madeleine, are "close to 400,000" and it may have generated as much as £1 million for the couple's fund.
A paperback edition with a new epilogue will be published on 10 May.