Amazon's coming tablet could feature an annual library subscription model that would let readers access older books, according to a report in the Wall Street Journal.

Citing unamed sources, the report said the library content would be available to Amazon's Prime customers, who currently pay £49 a year ($79 in the US) for unlimited two-day shipping for products purchased on Amazon.com as well as access to digital movies and TV shows on the site.

Selling for less than its worth

Amazon did not respond to a request to comment on the report.

Amazon, which sells the popular Kindle e-reader, is expected to unveil a touchscreen colour tablet in October or later. The company is expected to price the tablet at $300 (£190), less than is needed for a profit.

Amazon would make up for the lack of tablet profits by selling content, such as the digital library subscription for it, according to analysts. Forrester analyast Sarah Epps has predicted Amazon's tablet will have a 9-inch LCD touchscreen. Other analysts predict the tablet's screen will measure 7 inches.

Look out, Apple

Epps argues that Amazon's $300 price tag, along with the company's well-developed online market for selling books and other content, will present a challenge to Apple's successful iPad and iPad 2.

According to the Wall Street Journal's unnamed sources, Amazon would offer book publishers a fee for participating in the subscription program. The company would also limit the number of books an Amazon Prime customer could read without charge every month.

Amazon would still continue to sell new books individually, according to the report.