stop things breaking horribly if no planet atom.xml is present (e.g. with clean checkouts of the site)

aaargh, commit flood. I shouldn't leave debugging statements in when committing, I shouldn't leave debugging statements in when commiting, I shouldn't leave ...

from the better-late-than-never department, here's a stupidly overcomplex yet incomplete way of adding new books. Doesn't deal with tagging yet, but better than nothing, don't you think? Maybe someone else should rewrite the whole library component in an afternoon following KISS principles soon ;-)