Thanks for your answer, wallcraft. I'll go for a device supporting mobipocket then.
The Hanlin indeed looks interesting, thanks for pointing out that it can be bought in France. However I think I'll still go for the Cybook, for two reasons. First, it looks like I would have to buy the Hanlin from overseas, and this worries me in case I have to apply the warranty.
And then, I think dictionary support is important for me (though it's hard to tell since this would be my first reader). It turns out that I bought recently an awesome english dictionary in mobipocket format, and I'd really like to be able to use it with my reader!
Thanks again everybody for the clear answers!