Bonjour et bienvenue !
since you've been lurking for a while perhaps you know this already but just in case i'll mention it...
i wouldn't worry about the sony store. with
calibre and possibly a few drm-removal tools (google "convert lit" for example) you can get books at any ebookstore and convert them if necessary to lrf / epub. and more and more publishers are making their books available in epub format, which is good news for sony owners.
take a look in our own ebooks library for a lot of free ebooks already in the proper format (ebooks link in the blue menu bar).
and of course don't hesitate to stop by the
french forum for some good sources of ebooks in french, and friendly conversation.
also, since i see you are in paris, may i invite you to our next
mobileread apéro, the 31 january !
à bientôt !