[GeoffR]

Before you go to the trouble of installing hyphenation dictionaries, check if there are other reasons hyphenation might not be working:
- Some publishers disable hyphenation in the book. You may need to edit the book's stylesheet to reenable it.
- In kepubs, hyphenation may not be turned on unless you have the justification button set to full justification.

Edit: I just checked and the hyphenation dictionaries are missing from firmware 3.7.0, so I guess hyphenation won't work properly on the H2O unless you install the dictionaries yourself.