eBook readers in the UK, where we’ve enjoyed our pick of devices capable of displaying books purchased from any store we opt to buy from, may wish to exercise caution when it comes to the iPad’s eBook capabilities.

Apple’s insanely popular tablet offers a number of eBook apps including Apple’s own iBooks and Amazon’s Kindle app but early eBook adopters who’ve already amassed a library of eBooks from retailers such as Waterstones will find most (or all) of their books currently can’t be read by the device.

This is because eBooks sold by UK retailers tend to be protected by Adobe’s Digital Rights Management software which neither the iBook or Kindle apps support – although Apple DOES use the ePub eBook format it uses its own DRM system while Kindle uses its own format entirely.

Kindle owners – reportedly a tiny minority in the UK given Amazon’s late decision to release the device internationally – CAN read their existing titles on the iPad via the Kindle app and iPhone users will soon be able to access iBooks (with Apple promising bookmarks and notes being available across devices) but those with a reader from companies such as Sony or COOL-ER aren’t so lucky.

So where does this leave UK readers with a library of incompatible books?

While we’ve made no secret of our opinion that the best way of reading any eBook is on a dedicated device, history tells us that technical superiority doesn’t always win the day and with 2 million iPads already sold the signs are that Apple’s tablet is going to become the dominant force in mobile reading.

Market pragmatism suggests that companies such as Waterstones – who have led the UK eBook market – and other UK retailers will eventually need to look to the iPad for future sales. The simplest way of doing this would be to release Adobe DRM-capable apps which allow users both to access existing purchases and download new titles direct to the device.

Currently there no official signs that the any of the UK retailers are planning to do this but with Apple already claiming a 22% share of the US eBook market smart money has to be on UK retailers taking action to protect their sales.

In the meantime buyers should beware that books purchased via the iBooks or app can only be read on other iPads (and iPhones from later this month) while Kindle books require either a device with the Kindle app or an actual Kindle reader. Both can be a little pricey should you need to replace one at short notice .

If you’re looking for a reader which can cope with books from a wide range of retailers which in turn can be easily transferred to a new device, a standalone dedicated reader is still your best bet.