Poll - are there any good prequels?

[jack]

This came up in the pub last night with the scifi society -- are there any good prequels, preferably scifi/fantasy? We thought of:

Children's books where the prequal is written second out of a series: Magician's Nephew, Charmed Life.
Series written out of order, such as Hornblower, Small Gods in TP.
Retrospective prequels: Asimov's robot stories became prequels to his foundation novels, though weren't at the time.

I decided that it's because prequels generally get written when an author (or their heirs) runs out of ideas, even more so than sequels, but if that's not the case they're by no means inherantly bad.

Can you think of any others?

Comments

[filecoreinuse.livejournal.com]

Prelude to Foundation?

[filecoreinuse.livejournal.com]

Or in fact almost every other book set in the Foundation Universe.

[cartesiandaemon.livejournal.com]

I thought Prelude was ok but not really up to the standard of Foundation.