and here are some discussions of the word in french, because actually the same question is raised there as well ("what do we call these things ?") :
http://www.irenedelse.com/2008/02/25...-en-numerique/
Irène Delse is a writer and member of MR.
http://www.archicampus.net/wordpress/?p=206
note also that both François Bon and Alain Pierrot (both very active in the ebook world, and Alain Pierrot has been to two of our paris meetups

) use "liseuse"
François Bon :
http://www.tierslivre.net/spip/spip.php?article1872
interview with Alain Pierrot (his blog is currently under construction
http://www.apsed.com/blog/ )
http://lafeuille.homo-numericus.net/...n-pierrot.html