Lost 1/3 of my batterylife since yesterday---book got stuck downloading from 'archives' to ' home'.
Option 'View Downloading Items' , was
not greyed out and when I looked again after half an hour, it remained in limbo = downloading for ever.
Restarted the Kindle (home--menu--settings--menu--restart) and the book reappeared in 'archives' and could be downloaded 'home'.
Another thing to check (apart from indexing) when my battery drains quickly.