Ereaders are, apparently, going to be one of the hit technologies of 2010. There are certainly more to choose from today than there were a year ago, and in the UK you can even buy them in bookshops. Sony may have started the whole trend off here, but there are many companies jostling for a position at the front of the pack, and Bookeen is one of them.

Its Cybook Opus is a neat and tidy, no frills e-reader that does its job extremely well. The reader runs a Linux based operating system and supports plenty of formats including DRM and non-DRM Adobe PDF and ePUB files, DRM and non-DRM Mobipocket files, HTML, TXT, JPG, PNG and GIF file formats.

The 1GB of onboard storage can be augmented with microSD cards should you need more space, though Bookeen says that 1GB is room enough for 1,000 books.

Unlike some ereaders, the Cybook Opus does not play music files. Those who like to listen to tunes while they read will thus need to resort to a separate music player. The good news on that front is that the battery is entirely dedicated to presenting you with text to read, and the E-Ink based screen is very energy efficient. A full charge should keep you going for 8,000 page turns. You charge the battery via miniUSB and it'll charge while connected to your PC or the mains. We really like the fact that you can replace the battery, as it sits behind a removable backplate.

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Some may find the 5-inch screen a little small for their liking, and its four greyscales don't match the range reached by many other readers. But we found the size fine and the 600 x 800 pixels able to deliver crisp text. We also really like the existence of a sensor in the Cybook Opus that means the screen rotates between wide and tall formats as you turn it in your hands.

The small screen means that the Cybook Opus is easy to transport around. At 151 x 108 x 10mm it will fit into some pockets, and at 150g it is not a burden to carry. It comes with a slip case that adds to the dimensions but protects the screen from scratches.

There are few buttons. Two tall ones cater for moving between pages, while a D-pad gives you a more rounded set of directional movements. There's a back button and a menu button, the latter giving access to features like sorting the stored books by various criteria such as title, date and even file size.

With no really fancy features, and a small and pocket-friendly design, the Cybook Opus is one of the best ereaders we have seen.