But the controversy that exploded across social media has only sparked renewed interest in Bao Ninh's haunting classic and forced bookstores to scramble to keep pace with surging demand.

"I only knew about this novel because of these online discussions," said Le Hien, 25, who tried to buy the book at several bookstores in the capital Hanoi this week but found they were all out of stock.

"I was very surprised the book was sold out that quickly. I couldn't believe its sales went crazy," he told AFP.

First published in 1987 as "The Destiny of Love", the novel is narrated by a young North Vietnamese soldier who, like Ninh himself, served in a battalion that was almost entirely wiped out.

He is stalked by memories of the "jungle of screaming souls" and tortured by thoughts of his girlfriend's rape by fellow North Vietnamese men.

The book was met with instant acclaim abroad and controversy at home, where most war literature emphasised valour and sacrifice over cruelty and suffering.

The novel's inclusion in the 50-best list in late November touched off another round of recrimination even as it flew off shelves.

"This book has been debated for ages," said Nguyen, a bookseller on Hanoi's Nguyen Xi book street, who gave only his first name for fear of inviting backlash against his store.

"It has always sold steadily. It has never sold out like it did this time, though."

- Deeper truth -

Nguyen Thanh Tuan, a former head of the military's propaganda department, wrote on Facebook earlier this month that the novel "aimed to diminish the heroism of our army... fabricating and distorting the truth of the heroic struggle and immense sacrifices of millions of people".

Tuan's post calling for the honour to be revoked received thousands of likes and ricocheted across social media, garnering support especially from war veterans.

But many others defended the decision to honour the book.

"If we demand that a novel function like a battle report, we are forcing literature to perform the work of another profession," said literary critic Ha Thanh Van.

"The Sorrow of War" continues to move readers nearly 40 years after its publication because it "delves into the dark corners of memory, where war continues to exist as haunting memories, traumas, lingering regrets", she said.

Ngoc Tran, a 12th grade student in Hanoi, said she didn't think the work "tarnishes the image of Vietnamese soldiers from the past".

"It just reveals more truth about human nature," she told AFP.

But while the debate has opened up old societal rifts, it has also propelled the book to new heights of visibility, especially among young readers like Tran, born after its initial publication.

"After the controversy about the award went viral online, more people became interested and started looking to buy (the book)," said bookseller Nguyen.

Another bookseller on the same street who declined to give his name said sales had been slow before the furore "but suddenly we're sold out".

AFP journalists found five copies of the book at Ngan Nga bookstore in the capital, but many other vendors had been cleared out.

Nguyen Hai Dang, an editor at Tre Publishing House which has a lifetime agreement with Ninh, was quoted in state media as saying the controversy had prompted a flurry of orders, causing the central warehouse to fall behind.

Dang said a planned reprinting was already underway, however, and that the publisher had run off 15,000 copies so far this year.

It has printed about 80,000 copies since its agreement began in 2011.

The novel is also an international bestseller and has been translated into more than 15 languages.