Amazon has revealed a new version of its Kindle e-reader, a re-designed device that it says is the thinnest and lightest Kindle the technology firm has ever made.

Called the Kindle Oasis, the eighth-generation of the e-reader has been made 30% thinner, with the battery and processor now placed down one side on the rear of the device, creating a ridge that serves as an ergonomic grip.

Amazon says this is a deliberate feature that creates a better holding position for one-handed reading, and makes it feel more like the spine of a book.

The new device will cost £269.99, making it the most expensive in the range, which Amazon called its "flagship" e-reader. It weighs only 131 grams - lighter than an iPhone 6s.

Amazon now has 4.4 million titles available in digital form on Kindle - one million of which are exclusive to Amazon - and the firm is estimated to have sold over 30 million Kindles since the device was launched in 2007.

Chief executive Jeff Bezos said: "To lean back and read for hours, you need a sanctuary from distraction."

Amazon says the aim of the Kindle is to reach the "gold standard of paper" in terms of size and weight, making the device almost invisible.

"We want Kindle to disappear, and Kindle Oasis is the next big step in that mission," Mr Bezos added.

"It's the most advanced Kindle we've ever built - thin and ultra-lightweight, it gets out of the way so you can lose yourself in the author's world."

The Oasis is only 3.4mm at its thinnest point behind the screen, and comes with a cover included that slots together with the grip on the rear using magnets to create a flat surface when attached.

The cases, which come in three colours, also contain a battery that combined with the built-in power gives a battery life of "months", Amazon says.

The e-commerce firm has increasingly branched out in to wider technology in recent years, making a smartphone as well as several generations of their Fire tablets.