A self-service library attracts a passer-by's attention in Beijing recently. Containing more than 400 books, it allows users to borrow and return books 24-hours a day. Lu Ming / China News Service

Self-service libraries are becoming increasingly popular with Beijing residents, with 50 having sprung up across the city over the past year and 100 more are expected to open in the coming months.

The 24-hour service allows readers to choose from 20,000 books housed in giant automatic machines scattered across the capital.

And the convenience of the service has proved popular, with self-service libraries being the source of 31.63 percent of all books borrowed from public libraries in Beijing's Chaoyang district since they were introduced last year.

Tao Jun, a publicity officer at the Chaoyang District Library, said the service was beneficial to readers.

"The book vending machine has extended library service hours and has fewer location limitations than its traditional counterpart," Tao said.

An additional 100 self-service libraries will be set up in highly populated areas in the capital by the end of the year as demand increases, she said.

A single self-service library, containing more than 400 books, resembles an ATM but is about the size of three cars. Borrowers can keep five books for up to four weeks at a time.

Readers can register with their ID card for a membership at a public library for 100 yuan ($16), allowing them to borrow books from both the city's traditional libraries and the new self-service machines.

When the self-service machine is running short of books or is damaged, the library will be informed through its data center and cameras installed in the remote device.

Li Anyin, a retired resident in Chaoyang district, said the self-service machines were very convenient and easy to use.

"I can return or borrow a book anytime of the day, even early in the morning before I go for a stroll in the garden," he said.

"Returning the books can be done in a flexible way and you no longer have to rush to have the books returned before the library closes."

Li said he has introduced two of his "morning strolling partners" to the new machines.

Despite the convenience, some residents complain that the machines' selection of books lacks variety.

"Leafing through the books, you can hardly find a English novel or any fiction," said Wang Yue, 24, a graduate from Beijing Foreign Studies University.

Tao said there is little demand for foreign language books.

"Most of the books available are Chinese fiction, biography, cookery and horticulture," said Tao. "However, the library will consider catering for different tastes and including more books."

Tao said the library will also consider allowing the public to use passports to register for library memberships, opening the service to foreign bookworms.

Shenzhen in Guangdong province, the first city in China to introduce the self-service library, now houses 160 machines, and 40 more are to be opened by the end of the year, according to Nie Changyou, an officer at the Shenzhen city bureau of culture, sport and tourism.

Li Xinliang, marketing director of Shenzhen Seaever Intelligent Technology Co, the company that makes the machines, said interest in the service is growing across the country.

"In 2008, we only received an order for 10 machines, but the demand soared to 180 in the year 2011," Li said.

"So far we have produced some 460 machines and, as the service is becoming increasingly popular nationwide, it is believed demand will soar."

Contact the writer at zhengxin@chinadaily.com.cn