This may not mean the end of all locks on books readable on Sony's device as the ePub format has an option to implement copyright controls.

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Take Spotify, the European start-up based in the UK. It hit on a subscription-based format to provide an a la carte option to listen to music.

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Now, with studio support split, dual-format is starting to look like a more viable option.

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On the desktop at least you've actually got the option to download the clip in MP4 format, though we couldn't find that feature on the mobile version.

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The books come in landscape format only (wide, not tall) and you get just one paper option.

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Betamax in which one format prevailed, but the analogy is poor because Sony, Betamax' main backer, had the more expensive option.

ENGADGET: Switched On: Seeking neutrality in the hi-def format war