Features on the site enable users to create personal online book catalogues by entering either ISBN codes or book titles, which will automatically call up book covers and summaries. Users can also make margin notes on the pages and post reviews. More importantly, they can identify other users who have the same books and keep track of their bookshelf updates.

Since its launch in April last year, the aNobii community has grown rapidly by word of mouth, starting with Sung's friends. Now, the site connects more than 37,000 users from around the world.

'The nature of social networks is viral,' Sung says. 'If people find something new that they like, they naturally tell their friends. Bloggers compete to be the first to spread the message about a new product.'

The site has a larger following abroad than in Hong Kong. Half the users are from Italy, followed by Taiwan. Hong Kong comes in a poor third. According to web information company Alexa.com, aNobii is the 239th most frequently visited website in Italy, but ranks 2,843rd in Hong Kong.

An economics graduate from the University of Michigan, Sung became interested in the power of online communities a few years ago after reading Gonzo Marketing, Christopher Locke's book on how user participation and support changes the nature of marketing and advertising on the internet compared with conventional mediums.

'I was so fascinated by the book's pioneering concept, I wanted to see who else bought the book in Hong Kong and if they'd started web ventures,' he says. 'But there wasn't a channel for me to find those people. The internet was the only solution.'

Deciding that most book lovers would share his curiosity and his wish to catalogue their ever-growing book collections, Sung set up mock webpages to test his ideas on friends before setting up aNobii. Its popularity encouraged him to quit his job with an online entertainment company last year to work full time on the site, which gets a commission when users buy books through it or it sends them to online retailers such as Amazon.

Although Sung envisaged aNobii as a global community, its appeal in Italy took him by surprise. 'I have no connection in Italy and don't even speak Italian,' he says. 'I'm keen to know how the spark in Italy started. That's the magic of the internet. You never know how it will unfold.'

Niki Costantini, a frequent user from Ravenna, Italy, describes her encounter with aNobii as 'a perfect case of serendipity' - the IT technician found a post about aNobii while browsing a cooking website and signed up last month.

Costantini was delighted to log her collection of 560 books, which range from poetry and crime fiction to history, biographies and cook books. 'I've always wanted to catalogue my books and now I can do it online,' she says. 'And the bonus is that I can share them, read other users' opinions, and get to know other people and about new books.'

She often finds that people in other countries share her tastes. 'It makes me feel like I'm part of a real worldwide community,' she says. 'At the end of the day, we're not so different.'

The website's original Chinese and English interfaces have been translated into several languages, including Italian, Spanish, German, Korean, Swedish, Japanese and Catalan, and aNobii is expected to feature another 10 languages before long.

Much of the translation was done by volunteers using Editgrid, a spreadsheet-style program developed by IT entrepreneur David Lee Keng-fai. Users took just 48 hours to complete the Italian translation. 'It's a collaborative effort by users,' Sung says. 'It's amazing because people do it on a voluntary basis.'

Meanwhile, some members of the book-loving community have moved from online chats to face-to-face meetings.

Lynn Huang, an accountant in Taiwan, recently organised a book giveaway during which she met several fellow users. 'I have so many books I decided to get rid of some,' she says. 'Rather than sell them, I thought it would be more meaningful to give them away, as long as the recipients liked the books.' Most wanted to pay, but Huang says she encouraged them to do charity work instead. 'I don't keep track of whether they really do it. It's all about trust. Many have become my friends and we have dinner from time to time.'

The website has provided a stimulating social network for Andrew Shuen Pak-man, research director at local think-tank Lion Rock Institute, since he signed up last year. It's easier to strike up meaningful conversations with people who share similar reading tastes, says Shuen, who met a couple of users after scanning their book lists and comments.

'When you get tired of meeting empty-headed people in clubs, you sit back and think, 'What's the one trait that goes furthest in guaranteeing a person to be interesting?' It has to be reading books,' he says.

Freelance copywriter Moar Chi-hang has also made friends by organising book swaps. 'I found a book that I wanted to read on a user's bookshelf a couple of months ago and asked if he would swap. I ended up getting two books from him for free,' he says.

In Italy, Costantini has set up a forum to organise gatherings for aNobii users around the country. 'It's natural to want to meet other people if you share the same passion, and reading is a real passion for us all,' she says.

They hope to hold the first get-together in autumn. Although they plan to arrange visits to literary fairs and other events related to books, Costantini says there won't be any special agenda. 'What we're going to do is what everybody usually does with friends: talk about everything, have a nice dinner or drink,' she says. 'After all, aNobii is a virtual community, people aren't.'