[Bertolt]

IMHO the question "Which ereader should I buy?" is the wrong question. I bought a Kobo to start with and followed that with a Pocket book Lux 623. The Kobo (bought from Ebay UK) clunked after 18 months. The Pocketbook is an excellent machine with all the extras which you really dont need but the way it sorted my books into Files (fiction, non fiction, travel etc) did not work for me.
The better question to ask is "Where is it best for me to buy my books from?". And the answer is "Amazon", because they have the best selection of books by a mile (or two). I buy all my books from Amazon and there are also over a milliion free ones on offer from them, so it makes sense to buy a Kindle. The Kindle is the Volkswagen of ereaders: it just works very well and is very durable. And it's not expensive. The basice Kindle is excellent value at 59 GBP in the UK and even the Paperwhite is only 99 GBP at the moment - the prices have just dropped!
Many of my books cost 99p and some less (some free). All of my books are cheaper than the paper editions. I often buy the Kindle Daily Deal books.
I live in Spain (Malaga) most of the year and have a much better choice of books than I ever had in England thanks to the Kindle. I bought my present Kindle in Spain from Amazon.es and am registered with an Amazon account in the UK - I pay in GBP. Of course the books are not epub but Kindle format but you can change epubs to mobi very easily using Calibre (free) and then they can be read on the Kindle too. The reality is that I rarely need to use Calibre because there are so many more books in Kindle format.
PS I share all my books with my partner. We have 6 reading devices in total including our PCs and tablets. Amazon allow you to download on up to 6 devices. If you have a tablet or PC , get the Kindle app, which is free, and start reading now. Make your mind up about the ereader later.