The Yotaphone has arrived in the UK, but this is no ordinary smartphone. Not only does it sport a 4.3-inch display on its front, it also boasts an 4.3-inch e-Ink display on its rear.

Billed as the first "always-on" smartphone, the Yotaphone sports a relatively modest array of specs including a 1.7GHz dual-core processor, 2GB of RAM, 32GB of storage, Android 4.2.2 Jelly Bean, 13MP camera and a 1800mAh battery.

It's that black and white e-Ink display which is the main feature here, allowing you to read books comfortably while consuming very little power. Yota claims that the Yotaphone's battery life is 7 to 10 times better than rivals when reading books.

The e-ink display isn't touch sensitive though, with simple controls hidden below the screen in a bar which you can swipe across to turn pages, flick to the next news article or scroll through your new notifications.

Price and battery life

At £419 SIM-free, the Russian-built Yotaphone isn't exactly cheap and the company admits that with moderate to heavy use of the colour screen on the front the phone's battery won't last a whole day.

That said though, if you're more conservative with your usage then the Yotaphone can last more than a day, with notifications, news and updates popping up on the rear screen and using very little power.

As a sweetener, anyone who purchases the first-generation Yotaphone will be eligible for a discount on the second-gen Yotaphone which is expected to launch later this year.

The second generation sports a fully touchscreen e-Ink display, a better located rear camera, larger battery and more slender design.