Dubbed "Chills and Thrills", the campaign promoted the works of 16 writers for four weeks. It worked, raising the combined sales of the authors by almost two thirds.
But HarperCollins did not learn about its success until six months later. "That's when unsold copies started to come back in from distributors and shops," recalled Lipika Bhushan, marketing manager at HarperCollins India. "That was the only way to figure out what we'd sold."
Even though publishing in India is an established and growing industry, it has proven difficult to quantify. No comprehensive estimate is available of the size of its English and vernacular language markets because of the huge number of "unorganised" publishers and retailers. Precise sales figures for individual titles are often difficult to obtain.
The quiet launch, two months ago, of Nielsen's Bookscan system will attempt to change that. Bookscan is already used in countries such as the United States, the United Kingdom and Australia. It pulls retail data from sales counters throughout the country and produces compiled sales figures that are visible across the industry.
As India's literacy rate improves (it rose from 52 per cent to 68 per cent between 1991 and 2008), publishers predict that India will become the world's largest market for English books within the next 10 years.
Already, India is the third-largest English book market, according to figures from the National Book Trust of India, and it is expanding every year. K Vaitheeswaran, the chief operating officer of IndiaPlaza.com, a leading online book vendor, said: "Some of it is a function of the fact that books are now available for Rs99 (Dh8), which is a suddenly affordable price point. A whole lot of people are buying books at that price".
Another factor is the rise in the country's English readership. Government figures showed a 74 per cent rise in enrolments in English-medium schools between 2003 and 2006, largely spurred by the burgeoning Indian middle class.
An author such as Chetan Bhagat, who writes easily accessible books for and about the middle class, can thus tap into that growing readership. Sales of his four books have run into the millions of copies.
The bar has shifted even for more sophisticated books. Six or seven years ago, a book was a bestseller if it sold 3,000 to 5,000 copies. Now, Ms Bhushan said, that metric stands at 10,000 or even 15,000 copies.
The absence of real-time sales data has, however, hindered publishers eager to design effective marketing strategies. Jeremy Neate, the London-based head of research and international development at Nielsen, had helped launch Bookscan in 1995-96 in the United Kingdom, and he recalls that the situation was much the same back then.
"There was a lot of misinformation out there, and everything was claimed to be a bestseller," Mr Neate said. With Bookscan, "the week after the book was printed, they could see first-week sales, or they could be prepared to reprint and restock, or they could see which retailers weren't doing a good job of selling."
Bookscan started in the United Kingdom, Mr Neate said, by covering 25 per cent of the market. It is now used in nearly 98 per cent of the market. Reaching that kind of penetration in India will be difficult.
The Indian book market is fragmented, populated by a few large retail chains, many hundreds of small, independent bookstores, and even more unorganised retailers hawking books on sidewalks or from mobile pushcarts. Even in the organised section of the trade, Mr Neate said, "we could only work with retailers with computerised stock control systems.
"We're just trying to ring-fence what we're trying to measure. You can't measure the unmeasurable", he said.
M Madhu, the category head for books at the pan-Indian Landmark chain of bookstores, said: "My guess is, Bookscan right now covers 35 to 40 per cent of mainline fiction and non-fiction, and it doesn't cover academic or institutional sales. So today it's not yet an even representation of the market. But we have to live with that, and we have to wait for it to grow."
What Bookscan has already proven, however, is "that the long tail in books has grown longer," Mr Vaitheeswaran said. "Of course you know the John Grisham and the Dan Brown books sell, but now we know that the books further down the tail are being read as well. That's the true reflection of reading tastes."