As far as I know, to use a straight index Postgres requires either
ORDER BY pages, description -- or --
ORDER BY pages DESC, description DESC.
If you want the results by pages DESC, description ASC, then you have to
make an index on an expression or define your own operator or something
esoteric like that. I would think the ability to have an index where the
columns don't all collate in the same direction would be an easy feature
to add.