As more people turn to internet shopping with physical stores closed during the coronavirus pandemic, online booksellers such as Amazon are struggling to meet the huge demand they are seeing due to restocking priority going to essential products.

Readers have been increasingly heading to social media to air complaints about their inability to order books online.

"I can't go out so I was going to order some books on Amazon, but I found all the ones I wanted were sold out," said one frustrated bibliophile.

Even new release titles that hit shelves earlier this year are sold out, and the increased demand has led to a surge in the price of secondhand books.

As publishers in Japan do not sell directly to stores, rather using distributors to consign their books to booksellers, titles can be listed as sold out even if stocks remain in warehouses, a representative of a publisher said.

Positively reviewed books have become scarce on Amazon, which began limiting book deliveries from publishers from March despite the demand, a source close to the matter said.

According to a sales representative from a major publisher, Amazon said it is refraining from placing additional orders of books as shipping companies are struggling to cope with the huge demand for delivery of other goods.

"(Online stores) need to prioritize daily essentials and sanitary goods," Amazon explained to one midsized publisher in an email.

Some publishers have expressed frustration that their products have been given a lower priority, while others have accepted that it is inevitable in the current situation.

But with Amazon, currently the largest bookseller in Japan in terms of sales, not placing additional orders and many physical bookstores closed under the state of emergency, the damage to publishers is significant.

"We are working to return to normal operations as soon as possible," said a spokesperson for Amazon.

"Even though Amazon began as a bookstore, books generate less profit than other products for the company. So Amazon probably regards books as necessary, but nonessential," said magazine journalist Hiroyuki Nariai on the e-commerce giant's standpoint.

With e-books still relatively unpopular in Japan -- in 2019 just 20 percent of sales, including manga and magazines, were made via digital book downloads -- publishers have had to look to other options.

Some have begun selling books directly to readers. Tokyo-based Akishobo Inc., reputed for publishing books in humanities and foreign nonfiction, opened its own online store in April and sells books currently unavailable on Amazon.

"We want to explore new ways of connecting readers with books, as we add another avenue of delivering books to readers," said an Akishobo staff member.

Also popular among readers is a service offered by e-hon, an online bookstore operated by major distributor Tohan Corp., which allows customers to support their favorite bookstores, even as they remain closed, by having books delivered.