Book retailer Barnes & Noble Inc unveiled an e-reader on Thursday with a screen that can glow in the dark, a move geared towards improving its position against Amazon.com.

The 6-inch (15-cm) touch-screen device, which will hit stores in early May for $139, lands in a market where Apple Inc and Amazon are battling with Barnes & Noble for customers who want to read books and magazines on small portable devices. Weighing just under 7 ounces (200 grams), it is Barnes & Noble’s lightest Nook yet and is aimed at people who want to read in the dark without a light.

To read in the dark with other e-readers that use electronic ink, consumers had to buy an external light that attached to the device. While Apple’s iPads have backlit screens, Barnes & Noble said its technology creates a better nighttime reading experience than an LCD screen because it throws off less light and will not disturb a reader’s partner who is trying to sleep.

While Barnes & Noble is first to market with a glowing e-reader, Amazon may be hot on its heels. The Internet retailer is working on releasing its own e-reader with a glowing screen, according to a report on April 6 from the blog TechCrunch. Amazon did not respond for comment on the report.

Fighting deep-pocketed Amazon has proved to be an expensive proposition for Barnes & Noble, as it has poured hundreds of millions into developing the Nook. In January, the retailer forecast a steeper net loss than expected for the fiscal year, as it continues to spend on the technology.

“We are investing a lot but we feel good that those investments will pay off,” Barnes & Noble Chief Executive William Lynch said in an interview on Thursday.