Walmart wants to become your new go-to store for digital books.

The big-box retailer said Tuesday it’s opening its first-ever e-books storefront, thanks to a partnership with Rakuten Kobo. Kobo’s library of 6 million digital titles will now be available on Walmart’s US website, supplementing Walmart’s existing selection of physical books. Walmart is also offering an audiobook subscription service for $9.99 — $5 less than Amazon’s rival Audible subscription.

The new e-books store augments Walmart’s push to expand its online selection, part of a digital sales growth strategy aimed at becoming a stronger competitor to Amazon, the leader in online retail. In July, Walmart expanded its online assortment of baby gear and this month partnered with Ellen DeGeneres on a new clothing line for Walmart.com.

Walmart unveiled in January a partnership with Tokyo-based retailer Rakuten to create an online grocery delivery service in Japan, as well as the US e-books store. That deal is part of Walmart’s broader effort to partner with Amazon rivals, including its voice-shopping work with Google and cloud-computing deal with Microsoft. By bringing together these companies, Walmart may find ways to catch up to Amazon’s e-commerce business.

Walmart’s move into e-books could be seen as Walmart directly challenging Amazon, since Amazon started as an online bookseller and it popularized the e-book format with its Kindle e-reader.

Walmart’s work to cultivate online has seen early success, with the company reporting a 40 percent jump in US e-commerce sales in its latest quarter. Those sales are still small compared to Walmart store sales, but show its heavy investments in online business are benefiting the company.

In addition to the new e-book library online, customers will be able to buy digital book cards in 3,500 Walmart stores. Walmart will also sell the Kobo e-reader online and in 1,000 of its stores.