If you have a kindle, you can get it on there for free in five parts: Les Misérables Tome 1, Fantine; Tome 2, Cosette; Tome 3, Marius; Tome 4, L'Idylle Rue Plumet et L'Épopée Rue Saint-Denis; and Tome 5, Jean Valjean.
It also looks as if you could pay to download those 5 parts off of Barnes and Noble, for the Nook e-reader, a couple dollars per part, I think.
This is for free, on the computer. You can read it, but it won't let me link straight to it, so I'll have to give you some somewhat confusing directions. Ready?
Click on this link http://groupugo.div.jussieu.fr/
, and click on "œurves" on the side, and then click on the "édition critique et génétique" link, which is next to the words "Les Misérables." This will bring you to a separate page. Click on the "consultation" bar next to the list, and then it brings you to a nice table of contents. Click on the one you like, and begin! And, what's nice about that one is that it also has Victor Hugo' original French rough drafts for you to read there, if you like.
Here's another place where you can read the book for free:
Tome 1: http://www.gutenberg.org/files/17489/17489-h/17489-h.htm
Tome 2: http://www.gutenberg.org/files/17493/17493-h/17493-h.htm
Tome 3: http://www.gutenberg.org/files/17494/17494-h/17494-h.htm
Tome 4: http://www.gutenberg.org/files/17518/17518-h/17518-h.htm
Tome 5: http://www.gutenberg.org/files/17519/17519-h/17519-h.htm
And if you want to listen to it, here's a place where a lady recorded herself reading the unabridged version, available for download: http://www.litteratureaudio.com/livre-audio-gratuit-mp3/hugo-victor-les-miserables.html
If you needed a hard copy, you'll probably end up paying a hefty sum, but I would suggest searching on amazon.fr for it.
Or, on amazon.com, it would cost you a lot, but you could purchase each separate hardback part. Here's an example of one: http://www.amazon.com/mis
Um..just copy and paste that last one. I'm bad with urls.
Were any of these what you were looking for? Hope it helped! Enjoy!
Note: I cannot find all the threads, but I believe the audiobook and the French rough drafts were first found by our friend on here Marianne.