Thank you very much everyone.
I think I might go for Kindle, but in the meantime I also found a review of another model of it:
http://reviews.cnet.com/e-book-reade...-35022792.html
The aticle says that Kindle Touch has got loudspeakers too, so is there any significant difference between Kindle Touch and Kindle Keyboard? If not, then I'd rather have the former for practical reasons: it is smaller.
As to the memory, I think I'll simply delete and copy books on Kindle once I've finished one (I guess with 3GB memory, it will be possible to hold 2-3 books on the hard disc, unless it's a
War and Peace type of book).