What have you been thinking about it? I loved that book in fifth grade; it taught me the names of so many angels.

Mostly about the way it subverts the tropes of the unicorns having been too stupid/stubborn to get on the ark, and about the way in which the unicorns basically go 'between' a la Pern, and also whether they or their passengers age in those winkings out between summonings.

I also liked the ways in which it made the unicorns something more akin to angels than to beasts and thus not in need of human intervention to survive. I have a literary kink for that sort of thing (see my fixation on Leviathan, Shor ha'Bor and The Ziz.